Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Standards Track                                  Orange
Expires: January 4, February 3, 2018                                   S. Sivakumar
                                                           Cisco Systems
                                                            July 3,
                                                          August 2, 2017

                   A

                    YANG Data Model Models for the DS-Lite
                   draft-ietf-softwire-dslite-yang-03
                   draft-ietf-softwire-dslite-yang-04

Abstract

   This document defines a YANG data model for the DS-Lite Address
   Family Transition Router (AFTR) and Basic Bridging BroadBand (B4)
   elements .

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 http://datatracker.ietf.org/drafts/current/.

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 4, February 3, 2018.

Copyright Notice

   Copyright (c) 2017 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
   (http://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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   2
   2.  DS-Lite YANG Data Model . Models  . . . . . . . . . . . . . . . . . .   3
   3.  DS-Lite AFTR YANG Module  . . . . . . . . . . . . . . . . . .   4
   4.  DS-Lite B4 YANG Module  . . .   9
   4. . . . . . . . . . . . . . . . .  10
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  39
   5.  13
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  39
   6.  13
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  40
   7.  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  40
     7.1.  14
     8.1.  Normative references  . . . . . . . . . . . . . . . . . .  40
     7.2.  14
     8.2.  Informative references  . . . . . . . . . . . . . . . . .  41  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  42  16

1.  Introduction

   This document defines a data model for DS-Lite [RFC6333], using the
   YANG data modeling language [RFC6020].  Both the Address Family
   Transition Router (AFTR) and Basic Bridging BroadBand (B4) elements
   are covered by this specification.

   DS-Lite deployment considerations are discussed in [RFC6908].

   This document follows the guidelines of [RFC6087].

   This document uses the common YANG types defined in [RFC6991].

1.1.  Terminology

   This document makes use of the terms defined in [RFC6333].

   The terminology for describing YANG data models is defined in
   [RFC6020].

1.2.  Tree Diagrams

   The meaning of the symbols in these diagrams is as follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Curly braces "{" and "}" contain names of optional features that
      make the corresponding node conditional.

   o  Abbreviations before data node names: "rw" means configuration
      (read-write), "ro" state data (read-only).

   o  Symbols after data node names: "?" means an optional node, "!" a
      container with presence, and "*" denotes a "list" or "leaf-list".

   o  Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

   o  Ellipsis ("...") stands for contents of subtrees that are not
      shown.

2.  DS-Lite YANG Data Model Models

   Figure 1 depicts the YANG data model for the AFTR and AFTR, while Figure 2
   shows the YANG data model for the B4 elements. element.

   The AFTR model supports enabling one or more instances of the AFTR
   function on a device; each instance is responsible for serving a
   group of B4s.  The data model assumes that each AFTR instance can: be
   enable/disabled, be provisioned with dedicated configuration data,
   and maintain its own mapping table.  The data model assumes that
   pools of IPv4 addresses can be provisioned to the AFTR.  These pools
   may be contiguous or non-contiguous.  Also, it assumes that an  The AFTR
   can either assign individual port numbers or port sets.

   This
   module augments the NAT module in [I-D.sivakumar-yang-nat].

   As such, this document assumes [RFC4787][RFC5382][RFC5508] are
   enabled by default.  Also, the data model relies on adheres to the
   recommendations in [RFC6888] and [RFC7857].  In addition,  Further, the data model
   supports state migration as per [RFC7785].

   PCP-related considerations are out of scope of the document.  A YANG
   data model for PCP is documented in [I-D.boucadair-pcp-yang].

module: ietf-dslite
    +--rw dslite-config
    |  +--rw dslite-aftr-config {aftr}?
    |  |  +--rw enable?                  boolean
    |  |  +--rw dslite-aftr-instances
    |  |     +--rw dslite-aftr-instance* [id]
    |  |        +--rw id                             uint32
    |  |        +--rw name?                          string
    |  |        +--rw dslite-aftr-ipv6-address* [address-id]
    |  |        |  +--rw address-id      uint32
    |  |        | ietf-dslite-aftr
  augment /nat:nat-module/nat:nat-instances/nat:nat-instance:
    +--rw ipv6-address?                  inet:ipv6-address
    |  |
    +--rw ipv4-address?                  inet:ipv4-address
    |  |
    +--rw tunnel-mtu?                    uint16
    |  |        +--rw external-ip-address-pool* [address-id]
    |  |        |  +--rw address-id          uint32
    |  |        |  +--rw external-ip-pool?   inet:ipv4-prefix
    |  |
    +--rw subscriber-mask?               uint8
    |  |
    +--rw nat-mapping-type?              enumeration
    |  | state-migrate?                 boolean
    +--rw nat-filtering-type?            enumeration
    |  | max-softwire-per-subscriber?   uint8
    +--rw port-quota                     uint16
    | mss-clamping
    |  +--rw exclude-ports* [id]
    |  | mss-clamping-enable?   boolean
    |  +--rw id mss-value?             uint16
    |  |        |  +--rw (port-type)?
    |  |        |     +--:(single-port-number)
    |  |        |     |  +--rw single-port-number?   inet:port-number
    |  |        |     +--:(port-range)
    |  |        |
    +--rw start-port-number?    inet:port-number
    |  |        | v6-v4-dscp-preservation?       boolean
  augment /nat:nat-module/nat:nat-instances/nat:nat-instance/nat:mapping-table/nat:mapping-entry:
    +--rw end-port-number?      inet:port-number
    |  | b4-ip-address?      inet:ipv6-address
    +--rw port-set
    |  |        | v6-dscp?            uint8
    +--rw port-set-enable?    boolean
    |  |        | internal-v4-dscp?   uint8
    +--rw port-set-size?      uint16
    |  |        | external-v4-dscp?   uint8

                Figure 1: YANG Data Model for DS-Lite AFTR

   module: ietf-dslite-b4
       +--rw port-set-timeout?   uint32
    |  | dslite-b4
          +--rw enable-app? enable?                boolean
    |  |        +--rw max-softwire-per-subscriber?   uint8
    |  |
          +--rw transport-protocol* [transport-protocol-id]
    |  |        | dslite-b4-instances
             +--rw transport-protocol-id    uint8
    |  | dslite-b4-instance* [id]
                +--rw new-mappings-rate-limit? id                         uint32
    |  |
                +--rw mss-clamping
    |  |        | name?                      string
                +--rw mss-clamping-enable?   boolean
    |  |        | aftr-ipv6-addr             inet:ipv6-address
                +--rw mss-value?             uint16
    |  | ipv4-address?              inet:ipv4-address
                +--rw port-allocation-type?          enumeration
    |  | tunnel-mtu?                uint16
                +--rw address-roundrobin-enable? v6-v4-dscp-preservation    boolean
    |  |        +--rw udp-lifetime?                  uint32
    |  |        +--rw tcp-idle-timeout?              uint32
    |  |        +--rw tcp-trans-open-timeout?        uint32
    |  |        +--rw tcp-trans-close-timeout?       uint32
    |  |        +--rw tcp-in-syn-timeout?            uint32
    |  |        +--rw fragment-min-timeout?          uint32
    |  |        +--rw icmp-timeout?                  uint32
    |  |        +--rw hold-down-timeout?             uint32
    |  |        +--rw v6-v4-dscp-preservation        boolean
    |  |        +--rw logging-info
    |  |        |  +--rw logging-enable?        boolean
    |  |        |  +--rw destination-address?   inet:ip-prefix
    |  |        |  +--rw destination-port?      inet:port-number
    |  |        |  +--rw (protocol)?
    |  |        |     +--:(syslog)
    |  |        |     |  +--rw syslog?                boolean
    |  |        |     +--:(ipfix)
    |  |        |     |  +--rw ipfix?                 boolean
    |  |        |     +--:(ftp)
    |  |        |        +--rw ftp?                   boolean
    |  |        +--rw notify-address-pool-usage
    |  |        |  +--rw pool-id?                     uint32
    |  |        |  +--rw notify-pool-hi-threshold     percent
    |  |        |  +--rw notify-pool-low-threshold?   percent
    |  |        +--rw ftp-alg-enable?                boolean
    |  |        +--rw tftp-alg-enable?               boolean
    |  |        +--rw sip-alg-enable?                boolean
    |  |        +--rw rtsp-alg-enable?               boolean
    |  |        +--rw h323-alg-enable?               boolean
    |  |        +--rw all-algs-enable?               boolean
    |  |        +--rw mapping-table
    |  |           +--rw mapping-entry* [index]
    |  |              +--rw index                  uint32
    |  |              +--rw status?                enumeration
    |  |              +--rw type?                  enumeration
    |  |              +--rw b4-ip-address          inet:ipv6-address
    |  |              +--rw internal-ip-address    inet:ipv4-prefix
    |  |              +--rw internal-port
    |  |              |  +--rw (port-type)?
    |  |              |     +--:(single-port-number)
    |  |              |     |  +--rw single-port-number?   inet:port-number
    |  |              |     +--:(port-range)
    |  |              |        +--rw start-port-number?    inet:port-number
    |  |              |        +--rw end-port-number?      inet:port-number
    |  |              +--rw external-ip-address    inet:ipv4-address
    |  |              +--rw external-port
    |  |              |  +--rw (port-type)?
    |  |              |     +--:(single-port-number)
    |  |              |     |  +--rw single-port-number?   inet:port-number
    |  |              |     +--:(port-range)
    |  |              |        +--rw start-port-number?    inet:port-number
    |  |              |        +--rw end-port-number?      inet:port-number
    |  |              +--rw transport-protocol     uint8
    |  |              +--rw lifetime               uint32
    |  |              +--rw v6-dscp?               uint8
    |  |              +--rw internal-v4-dscp?      uint8
    |  |              +--rw external-v4-dscp?      uint8
    |  |              +--rw description?           string
    |  +--rw dslite-b4-config {b4}?
    |     +--rw enable?                boolean
    |     +--rw dslite-b4-instances
    |        +--rw dslite-b4-instance* [id]
    |           +--rw id                         uint32
    |           +--rw name?                      string
    |           +--rw aftr-ipv6-addr             inet:ipv6-address
    |           +--rw ipv4-address?              inet:ipv4-address
    |           +--rw tunnel-mtu?                uint16
    |           +--rw v6-v4-dscp-preservation    boolean
    +--rw dslite-state
       +--ro dslite-aftr-state {aftr}?
       |  +--ro dslite-aftr-instances
       |     +--ro dslite-aftr-instance* [id]
       |        +--ro id                           int32
       |        +--ro name?                        string
       |        +--ro aftr-capabilities
       |        |  +--ro eim-support?                        boolean
       |        |  +--ro eif-support?                        boolean
       |        |  +--ro edm-support?                        boolean
       |        |  +--ro edf-support?                        boolean
       |        |  +--ro adm-support?                        boolean
       |        |  +--ro adf-support?                        boolean
       |        |  +--ro pcp-support?                        boolean
       |        |  +--ro subscriber-mask-support?            boolean
       |        |  +--ro port-set-support?                   boolean
       |        |  +--ro self-state-migration-support?       boolean
       |        |  +--ro mss-clamping-support?               boolean
       |        |  +--ro port-randomization-support?         boolean
       |        |  +--ro port-preservation-support?          boolean
       |        |  +--ro port-parity-preservation-support?   boolean
       |        |  +--ro transport-proto-capabilities* [transport-protocol-id]
       |        |  |  +--ro transport-protocol-id    uint8
       |        |  +--ro v6-v4-dscp-preservation-support?    boolean
       |        |  +--ro logging-support?                    boolean
       |        |  +--ro ftp-alg-support?                    boolean
       |        |  +--ro tftp-support?                       boolean
       |        |  +--ro sip-alg-support?                    boolean
       |        |  +--ro rtsp-alg-support?                   boolean
       |        |  +--ro h323-alg-support?                   boolean
       |        +--ro aftr-current-config
       |        |  +--ro dslite-aftr-ipv6-address* [address-id]
       |        |  |  +--ro address-id      uint32
       |        |  |  +--ro ipv6-address?   inet:ipv6-address
       |        |  +--ro ipv4-address?                  inet:ipv4-address
       |        |  +--ro tunnel-mtu?                    uint16
       |        |  +--ro external-ip-address-pool* [address-id]
       |        |  |  +--ro address-id          uint32
       |        |  |  +--ro external-ip-pool?   inet:ipv4-prefix
       |        |  +--ro subscriber-mask?               uint8
       |        |  +--ro nat-mapping-type?              enumeration
       |        |  +--ro nat-filtering-type?            enumeration
       |        |  +--ro port-quota                     uint16
       |        |  +--ro exclude-ports* [id]
       |        |  |  +--ro id                    uint16
       |        |  |  +--ro (port-type)?
       |        |  |     +--:(single-port-number)
       |        |  |     |  +--ro single-port-number?   inet:port-number
       |        |  |     +--:(port-range)
       |        |  |        +--ro start-port-number?    inet:port-number
       |        |  |        +--ro end-port-number?      inet:port-number
       |        |  +--ro port-set
       |        |  |  +--ro port-set-enable?    boolean
       |        |  |  +--ro port-set-size?      uint16
       |        |  |  +--ro port-set-timeout?   uint32
       |        |  +--ro enable-app?                    boolean
       |        |  +--ro max-softwire-per-subscriber?   uint8
       |        |  +--ro transport-protocol* [transport-protocol-id]
       |        |  |  +--ro transport-protocol-id    uint8
       |        |  +--ro new-mappings-rate-limit?       uint32
       |        |  +--ro mss-clamping
       |        |  |  +--ro mss-clamping-enable?   boolean
       |        |  |  +--ro mss-value?             uint16
       |        |  +--ro port-allocation-type?          enumeration
       |        |  +--ro address-roundrobin-enable?     boolean
       |        |  +--ro udp-lifetime?                  uint32
       |        |  +--ro tcp-idle-timeout?              uint32
       |        |  +--ro tcp-trans-open-timeout?        uint32
       |        |  +--ro tcp-trans-close-timeout?       uint32
       |        |  +--ro tcp-in-syn-timeout?            uint32
       |        |  +--ro fragment-min-timeout?          uint32
       |        |  +--ro icmp-timeout?                  uint32
       |        |  +--ro hold-down-timeout?             uint32
       |        |  +--ro v6-v4-dscp-preservation        boolean
       |        |  +--ro logging-info
       |        |  |  +--ro logging-enable?        boolean
       |        |  |  +--ro destination-address?   inet:ip-prefix
       |        |  |  +--ro destination-port?      inet:port-number
       |        |  |  +--ro (protocol)?
       |        |  |     +--:(syslog)
       |        |  |     |  +--ro syslog?                boolean
       |        |  |     +--:(ipfix)
       |        |  |     |  +--ro ipfix?                 boolean
       |        |  |     +--:(ftp)
       |        |  |        +--ro ftp?                   boolean
       |        |  +--ro notify-address-pool-usage
       |        |  |  +--ro pool-id?                     uint32
       |        |  |  +--ro notify-pool-hi-threshold     percent
       |        |  |  +--ro notify-pool-low-threshold?   percent
       |        |  +--ro ftp-alg-enable?                boolean
       |        |  +--ro tftp-alg-enable?               boolean
       |        |  +--ro sip-alg-enable?                boolean
       |        |  +--ro rtsp-alg-enable?               boolean
       |        |  +--ro h323-alg-enable?               boolean
       |        |  +--ro all-algs-enable?               boolean
       |        +--ro mapping-table
       |        |  +--ro mapping-entry* [index]
       |        |     +--ro index                  uint32
       |        |     +--ro status?                enumeration
       |        |     +--ro type?                  enumeration
       |        |     +--ro b4-ip-address          inet:ipv6-address
       |        |     +--ro internal-ip-address    inet:ipv4-prefix
       |        |     +--ro internal-port
       |        |     |  +--ro (port-type)?
       |        |     |     +--:(single-port-number)
       |        |     |     |  +--ro single-port-number?   inet:port-number
       |        |     |     +--:(port-range)
       |        |     |        +--ro start-port-number?    inet:port-number
       |        |     |        +--ro end-port-number?      inet:port-number
       |        |     +--ro external-ip-address    inet:ipv4-address
       |        |     +--ro external-port
       |        |     |  +--ro (port-type)?
       |        |     |     +--:(single-port-number)
       |        |     |     |  +--ro single-port-number?   inet:port-number
       |        |     |     +--:(port-range)
       |        |     |        +--ro start-port-number?    inet:port-number
       |        |     |        +--ro end-port-number?      inet:port-number
       |        |     +--ro transport-protocol     uint8
       |        |     +--ro lifetime               uint32
       |        |     +--ro v6-dscp?               uint8
       |        |     +--ro internal-v4-dscp?      uint8
       |        |     +--ro external-v4-dscp?      uint8
       |        |     +--ro description?           string
       |        +--ro statistics
       |        |  +--ro traffic-statistics
       |        |  |  +--ro sent-packet?      yang:zero-based-counter64
       |        |  |  +--ro sent-byte?        yang:zero-based-counter64
       |        |  |  +--ro rcvd-packet?      yang:zero-based-counter64
       |        |  |  +--ro rcvd-byte?        yang:zero-based-counter64
       |        |  |  +--ro dropped-packet?   yang:zero-based-counter64
       |        |  |  +--ro dropped-byte?     yang:zero-based-counter64
       |        |  +--ro mapping-table-stats
       |        |     +--ro current-mt-size?       yang:zero-based-counter64
       |        |     +--ro max-mt-size?           uint32
       |        |     +--ro total-tcp-mappings?    uint32
       |        |     +--ro total-udp-mappings?    uint32
       |        |     +--ro total-icmp-mappings?   uint32
       |        +--ro available-capacity-client?   percent
       |        +--ro available-capacity-ext?      percent
       |        +--ro address-pool-in-use?         percent
       |        +--ro port-in-use?                 percent
       +--ro dslite-b4-state {b4}?
          +--ro dslite-b4-instances
             +--ro dslite-b4-instance* [id]
                +--ro id                 int32
                +--ro name?              string
                +--ro b4-capabilities
                |  +--ro ipv4-address-modify?               boolean
                |  +--ro tunnel-mtu-support?                boolean
                |  +--ro v6-v4-dscp-preservation-support    boolean
                +--ro b4-state
                   +--ro status?                            boolean
                   +--ro aftr-ipv6-addr                     inet:ipv6-address
                   +--ro ipv4-address-configured?           inet:ipv4-address
                   +--ro v6-v4-dscp-preservation-enabled?   boolean

  notifications:
    +---n dslite-aftr-event
       +--ro id?                      -> /dslite-state/dslite-aftr-state/dslite-aftr-instances/dslite-aftr-instance/id
       +--ro notify-pool-threshold    percent

                Figure 1: YANG Data Model for DS-Lite AFTR

3.  DS-Lite YANG Module

  <CODE BEGINS> file "ietf-dslite@2017-07-03.yang"

  module ietf-dslite {
      namespace "urn:ietf:params:xml:ns:yang:ietf-dslite";
      prefix dslite;

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

      organization "Softwire Working Group";
      contact
       "Mohamed Boucadair <mohamed.boucadair@orange.com>
        Christian Jacquenet <christian.jacquenet@orange.com>
        Senthil Sivakumar <ssenthil@cisco.com>";

     description
        "This module is a YANG module for DS-Lite AFTR/B4
        implementations.

        Copyright (c) 2017 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 2017-07-03 {
        description "Fix some minor points.";
         reference "-ietf-03";
      }

      revision 2017-01-03 {
        description "Fixed a compilation error:
          https://github.com/mbj4668/pyang/issues/296.";
         reference "-ietf-02";
      }

      revision 2016-11-14 {
        description "Integrates the comments from Ian:
        add B4 module, add an MSS leaf, add more details about
        logging protocols, and other edits.";
         reference "-ietf-01";
      }

      revision 2016-07-27 {
        description "-00 IETF version.";
         reference "-ietf-00";
      }

      revision 2016-06-13 {
        description "Update the module.";
         reference "-04";
      }

      revision 2015-12-16 {
        description "Fix an error.";
         reference "-03";
      }

      revision 2015-09-01 {
        description "Add port threshold notifications.";
         reference "-02";
      }

      revision 2015-08-31 {
        description "Fix a timeout issue.";
         reference "-01";
      }

      revision 2015-08-17 {
        description "First spec.";
         reference "-00";
      }

  // Typedef

  typedef percent {
      type uint8 {
              range "0 .. 100";
      }
      description
          "Percentage";
  }

  // FEATURES

    feature aftr {
      description
      "An AFTR element is the combination of
      an IPv4-in-IPv6 tunnel endpoint and an
      IPv4-IPv4 NAT implemented on the same node.";

     reference
        "RFC6333";
    }

    feature b4 {
      description
      "The B4 element is a function implemented
      on a dual-stack-capable node, either a directly
      connected device or a CPE, that creates
      a tunnel to an AFTR.";

     reference
        "RFC6333";
    }

  /*
   * Grouping
   */

  // port numbers: single or port range

  grouping port-number {
      description
          "Individual port or a range of ports.";

      choice port-type {
          default single-port-number;
          description
              "Port type: single or port-range.";

          case single-port-number {
              leaf single-port-number {
                  type inet:port-number;
                  description
                      "Used for single port numbers.";
              }
          }

          case port-range {
              leaf start-port-number {
                  type inet:port-number;
                  description
                      "Beginning of the port range.";
              }

              leaf end-port-number {
                  type inet:port-number;
                  description
                      "End of the port range.";
              }
          }
      }
  }

  // Timeout variables

  grouping lifetime {
     description
      "Configure values of various timeouts.";

      leaf udp-lifetime {
          type uint32;
          units "seconds";
          default 120;
          description
              "UDP inactivity timeout [RFC4787].";
      }

      leaf tcp-idle-timeout {
          type uint32;
          units "seconds";
          default 7440;
          description
              "TCP Idle timeout as per [RFC5382] should be no
               more than 2 hours and 4 minutes.";
      }

      leaf tcp-trans-open-timeout {
          type uint32;
          units "seconds";
          default 240;
          description
            "The value of the transitory open connection
            idle-timeout.
            Section 2.1 of [RFC7857] clarifies that a NAT
            should provide different configurable
            parameters for configuring the open and
            closing idle timeouts.
            To accommodate deployments that consider
            a partially open timeout of 4 minutes as being
            excessive from a security standpoint, a NAT may
            allow the configured timeout to be less than
            4 minutes.
            However, a minimum default transitory connection
            idle-timeout of 4 minutes is recommended.";
      }

      leaf tcp-trans-close-timeout {
          type uint32;
          units "seconds";
          default 240;
          description
            "The value of the transitory close connection
            idle-timeout.
            Section 2.1 of [RFC7857] clarifies that a NAT
            should provide different configurable
            parameters for configuring the open and
            closing idle timeouts.";
      }

      leaf tcp-in-syn-timeout {
          type uint32;
          units "seconds";
          default 6;
          description
            "6 seconds, as defined in [RFC5382].";
      }

      leaf fragment-min-timeout {
          type uint32;
          units "seconds";
          default 2;
          description
            "As long as the AFTR has available resources,
            the AFTR allows the fragments to arrive
            over fragment-min-timeout interval.

            The default value is inspired from RFC6146.";
      }

      leaf icmp-timeout {
          type uint32;
          units "seconds";
          default 60;
          description
              "60 seconds, as defined in [RFC5508].";
      }

      leaf hold-down-timeout {
          type uint32;
          units "seconds";
          default 120;
          description
              "Hold down timer. Ports in the
              hold down pool are not reassigned until
              this timer expires.
              The length of time and the maximum
              number of ports in this state must be
              configurable by the administrator
              [RFC6888]. This is necessary in order
              to prevent collisions between old
              and new mappings and sessions. It ensures
              that all established sessions are broken
              instead of redirected to a different peer.
              The default value is defined in REQ#8
              from [RFC6888].";
      }
  }
  // AFTR Parameters

  grouping aftr-parameters {

      description
         "A set of AFTR parameters";

      list dslite-aftr-ipv6-address {

          key address-id;

          description
            "set one or multiple IP addresses for
             the dslite-aftr";

          leaf address-id {
             type uint32;
             description
                "The identifier of the address";
          }

           leaf ipv6-address {
             type inet:ipv6-address;
             description
               "IPv6 address of the dslite-aftr.";
          }
      }
      leaf ipv4-address {
          type inet:ipv4-address;
          default "192.0.0.1";
          description
            "IPv4 address of the DS-Lite AFTR.
            192.0.0.1 is reserved for the AFTR element
            [RFC6333].
            This address can be used to report ICMP
            problems and will appear in traceroute
            outputs.";
      }

      leaf tunnel-mtu {
          type uint16;
          description
              "Configures a tunnel MTU.
              [RFC6908] specifies that since
              fragmentation and reassembly is not
              optimal, the operator should do
              everything possible to eliminate
              the need for it.  If the operator uses
              simple IPv4-in-IPv6 softwire, it is
              recommended that the MTU size of the IPv6
              network between the B4 and the AFTR
              accounts for the additional overhead
              (40 bytes).";
      }

      list external-ip-address-pool {

          key address-id;

          description
           "Pool of external IP addresses used to service
            internal hosts.
            Both contiguous and non-contiguous pools
            can be configured to an AFTR.
            Refer to REQ-3 of [RFC6888].";

          leaf address-id {
              type uint32;
              description
                "An identifier of the address.";
          }

          leaf external-ip-pool {
              type inet:ipv4-prefix;
              description
                "An IPv4 prefix used by the AFTR
                 for NAT purposes.";
          }
      }

      leaf subscriber-mask {
          type uint8 {
              range "0 .. 128";
              }
          default "56";
          description
              "The subscriber-mask is an integer that indicates
               the length of significant bits to be applied on
               the source IPv6 address (internal side) to
               unambiguously identify a CPE.

               Subscriber-mask is a system-wide configuration
               parameter that is used to enforce generic
               per-subscriber policies (e.g., port-quota).

               The enforcement of these generic policies does not
               require the configuration of every subscriber's prefix.

               Example: suppose the 2001:db8:100:100::/56 prefix is
               assigned to a DS-Lite enabled CPE. Suppose also that the
               2001:db8:100:100::1 is the IPv6 address used by the
               B4 that resides in that CPE. When the AFTR
               receives a packet from this client,
               it applies the subscriber-mask (e.g., 56) on
               the source IPv6 address to compute the associated prefix
               for this client (that is 2001:db8:100:100::/56).  Then,
               the AFTR enforces policies based on that prefix
               (2001:db8:100:100::/56), not on the exact
               source IPv6 address [RFC7785].";
      }

     leaf nat-mapping-type {
             type enumeration {
                     enum "eim"  {
                         description
                             "Endpoint-Independent-Mapping.
                             Refer to Section 4 of [RFC4787].";
                           }

                      enum "adm"  {
                          description
                             "Address-Dependent-Mapping.
                              Refer to Section 4 of [RFC4787].";
                            }

                        enum "edm"  {
                            description
                              "address-and-port-Dependent-Mapping.
                               Refer to Section 4 of [RFC4787].";
                            }
                          }
                     description
                        "Indicates the type of the NAT mapping.";
      }

      leaf nat-filtering-type {
               type enumeration {
                     enum "eif"  {
                        description
                           "Endpoint-Independent-Filtering.
                           Refer to Section 5 of [RFC4787].";
                         }

                      enum "adf"  {
                           description
                              "Address-Dependent-Filtering.
                              Refer to Section 5 of [RFC4787].";
                      }

                      enum "edf"  {
                        description
                            "address-and-port-Dependent-Filtering.
                             Refer to Section 5 of [RFC4787].";
                            }
                       }
            description
              "Indicates the type of the NAT filtering.";
      }

      leaf port-quota {
          type uint16;
          mandatory true;
          description
            "Configures a port quota to be assigned per
            subscriber.
            According to [RFC6888], per-subscriber limits
            must be configurable by the administrator.";
      }

      list exclude-ports {
          key "id";
          description
             "The set of ports not to be assigned
              by the AFTR.";

          leaf id {
              type uint16;
              description
                "An identifier";
          }

          uses port-number;
      }

      container port-set {
          description
            "Manages port-set assignments.";

          leaf port-set-enable {
            type boolean;
             description
              "Enable/Disable port set assignment.";
          }

          leaf port-set-size {
            type uint16;
            description
              "Indicates the size of assigned port sets.";
          }

          leaf port-set-timeout {
            type uint32;
            description
            "Inactivity timeout for port sets.";
          }
      }

      leaf enable-app {
          type boolean;
          default true;
          description
          "Enable/disable the IP address
          pooling behavior of Paired (APP).
          APP is recommended in REQ-2 from
          [RFC4787].";
      }

      leaf max-softwire-per-subscriber {
          type uint8;
          default 1;
          description
          "Configures the maximum softwire per subscriber
          feature as per Section 4 of [RFC7785].

          A subscriber is uniquely identified by means
          of subscriber-mask.

          This policy aims to prevent a misbehaving
          subscriber from mounting several DS-Lite
          softwires that would consume additional AFTR
          resources (e.g., get more external ports if
          the quota were enforced on a per-softwire basis,
          consume extra processing due to a large number
          of active softwires).";
      }

      list transport-protocol {
          key "transport-protocol-id";
          description
            "Set of (transport) protocols supported by
            the AFTR. Default must be set to
            TCP and UDP.";

          leaf transport-protocol-id {
              type uint8;
              description
                 "Identifier of the transport protocol.
                 IANA Protocol Numbers maintained in
                 http://www.iana.org/assignments/
                 protocol-numbers are used.";
          }
      }

      leaf new-mappings-rate-limit {
          type uint32;
          description
           "Rate-limit sessions per subscriber.
           The goal is to prevent a single subscriber
           from consuming excessive CPU resources from
           the AFTR.";
      }

      container mss-clamping {
          description
            "Manages port-set assignments.";

          leaf mss-clamping-enable {
             type boolean;
             description
               "Enable/disable MSS rewriting feature.";
          }

          leaf mss-value {
            type uint16;
            units "octets";
            description
              "Sets the MSS value to be used for
               MSS rewriting.";
          }
       }

                 leaf port-allocation-type {
                      type enumeration {
                          enum "random"  {
                             description
                                "Port port randomization.";
                          }

                          enum "port-preservation"  {
                             description
                     "Indicates whether the PCP server should
                       preserve the internal port number.";
                          }

                          enum "port-range-preservation"  {
                             description
                        "Indicates whether the NAT device should
                      preserve the internal port range.";
                          }

                          enum "port-parity-preservation"  {
                             description
                     "Indicates whether the PCP server should
                       preserve the port parity of the
                       internal port number.";
                          }
                       }
                      description
                        "Indicates the type of a port allocation.";
                 }

      leaf address-roundrobin-enable {
         type boolean;
         description
            "Enable/disable address allocation
            round robin.";
      }

      uses lifetime;

      leaf v6-v4-dscp-preservation {
          type boolean;
          mandatory true;
          description
           "Copies the DSCP value from the IPv6 header
           and vice versa.
           According to Section 2.10 of [RFC6908],
           operators should use this model
           by provisioning the network such that
           the AFTR copies the DSCP value in the IPv4
           header to the Traffic Class field in
           the IPv6 header, after the encapsulation
           for the downstream traffic.";
      }

      container logging-info {
           description
              "Information about AFTR logging events.";

          leaf logging-enable {
               type boolean;
               description
                 "Enable logging features as per Section 2.3
                 of [RFC6908].";
          }

          leaf destination-address {
               type inet:ip-prefix;
               description
                   "Address of the collector that receives
                   the logs.";
          }
          leaf destination-port {
               type inet:port-number;
               description
                  "Destination port of the collector.";
          }

      choice protocol {

          description
              "Enable the protocol to be used for
               the retrieval of logging entries.";

          case syslog {
              leaf syslog {
                  type boolean;
                  description
                      "Used if SYSLOG is in use.";
              }
          }

          case ipfix {
              leaf ipfix {
                  type boolean;
                  description
                      "Used if IPFIX is in use.";
              }
          }

          case ftp {
              leaf ftp {
                  type boolean;
                  description
                      "Used if FTP is in use.";
              }
          }
       }
      }

      container notify-address-pool-usage {
            description
               "Notification of Pool usage when certain criteria
                is met.";

            leaf pool-id {
                 type uint32;
                 description
                     "Pool-ID for which the notification criteria is
                      defined.";

            }

            leaf notify-pool-hi-threshold {
                 type percent;
                 mandatory true;
                 description
                   "Notification must be generated when the defined
                   high threshold is reached. For example, if a
                   notification is required when the pool utilization
                   reaches 90%, this configuration parameter must be
                   set to 90%.";
            }

            leaf notify-pool-low-threshold {
                 type percent;
                 description
                   "Notification must be generated when the defined
                   low threshold is reached. For example, if a
                   notification is required when the pool utilization
                   reaches below 10%, this configuration parameter
                   must be set to 10%.";
            }
       }

            leaf ftp-alg-enable {
                 type boolean;
                 description
                    "Enable/Disable FTP ALG.";
            }

            leaf tftp-alg-enable {
                 type boolean;
                 description
                    "Enable/Disable TFTP ALG.";
            }

            leaf sip-alg-enable {
                 type boolean;
                 description
                    "Enable/Disable SIP ALG.";
            }

            leaf rtsp-alg-enable {
                 type boolean;
                 description
                    "Enable/Disable RTSP ALG.";
            }
            leaf h323-alg-enable {
                 type boolean;
                 description
                    "Enable/Disable H323 ALG.";
            }

            leaf all-algs-enable {
                 type boolean;
                 description
                    "Enable/Disable all the ALGs.";
            }
  }

  // Mapping Entry (Extended NAT44 mapping Entry)

  grouping mapping-entry {
     description
       "A DS-Lite AFTR mapping entry.";

     leaf index {
         type uint32;
         description
           "A unique identifier of a mapping entry.";
     }

     leaf status {
          type enumeration {

          enum "disabled"  {
             description
                "The mapping entry is not in use (Disabled).";
            }

          enum "assigned" {
             description
                "This mapping has been granted by the server.";
          }

          enum "stale" {
             description
                "This is a stale mapping (case of reboot).";
          }
         }
         description
            "Indicates the status of a mapping entry.";
      }

     leaf type {
          type enumeration {

          enum "static"  {
             description
                "The mapping entry is manually configured.";
            }

          enum "implicit" {
             description
                "This mapping is created by an outgoing packet.";
          }

          enum "explicit" {
             description
              "This is a dynamic explicit mapping created as a result
              of a PCP operation.";
          }
         }
         description
            "Indicates the type of a mapping entry. E.g.,
            a mapping can be: static, dynamic implicit, or
            dynamic explicit.";
      }

      leaf b4-ip-address {
          type inet:ipv6-address;
          mandatory true;
          description
              "Corresponds to the IPv6 address
              used by the B4 element.";
       }

      leaf internal-ip-address {
          type inet:ipv4-prefix;
          mandatory true;
          description
           "Corresponds to the source IPv4 address
            of the IPv4 packet conveyed over the softwire.";
       }

      container internal-port {
          description
             "Corresponds to the source port of the
             IPv4 packet conveyed over the softwire.";
           uses port-number;
      }

     leaf external-ip-address {
          type inet:ipv4-address;
          mandatory true;
          description
           "External IPv4 address assigned by the AFTR.";
     }

     container external-port {
          description
              "External port number assigned by the AFTR.";
          uses port-number;
     }

     leaf transport-protocol {
         type uint8;
         mandatory true;
         description
           "Upper-layer protocol associated with this mapping.
            Values are taken from the IANA protocol registry.
            For example, this field contains 6 (TCP) for a TCP
            mapping or 17 (UDP)

                 Figure 2: YANG Data Model for a UDP mapping.";
     }

     leaf lifetime {
          type uint32;
          units "seconds";
          mandatory true;
          description
            "Lifetime of the mapping.";
     }

     leaf v6-dscp {
          type uint8;
          description
            "DSCP value used at the softwire level
            (i.e., IPv6 header).";
     }

     leaf internal-v4-dscp {
          type uint8;
          description
            "DSCP value of the encapsulated IPv4 packet.";
     }

     leaf external-v4-dscp {
          type uint8;
          description
            "DSCP value of the translated IPv4 packet
             as marked by the AFTR.";

     }

     leaf description {
          type string;
          description
           "A description string associated with the mapping.";
     }
  }

  /*
    * DS-Lite AFTR Configuration
    */

  container dslite-config {

      description
       "AFTR and B4 configuration.";

  container dslite-aftr-config {
      if-feature aftr;

      description
       "dslite-aftr";

      leaf enable {
          type boolean;
          description
           "Enable/Disable dslite-aftr function.";
      }

      container dslite-aftr-instances {
         description
           "dslite-aftr instances";

          list dslite-aftr-instance {
              key "id";
                description
                  "A dslite-aftr instance.";

             leaf id {
                type uint32;
                description
                  "dslite-aftr instance identifier.";
             }

             leaf name {
                type string;
                description
                  "A name associated with the dslite-aftr instance.";
             }

             uses aftr-parameters;

             container mapping-table {
                description
                  "dslite-aftr mapping table maintained by
                    the dslite-aftr server.";

                  list mapping-entry {
                    key "index";
                    description
                      "dslite-aftr mapping entry.";
                    uses mapping-entry;
                 }
              }
          }
      }
  }

  /*
    *

3.  DS-Lite B4 Configuration
    */
  container dslite-b4-config {
      if-feature b4;
      description
       "dslite-b4";

      leaf enable {
          type boolean;
          description
           "Enable/Disable dslite-b4 function.";
      }

      container dslite-b4-instances {
         description
           "dslite-b4 instances";

          list dslite-b4-instance {
              key "id";
                description
                  "a dslite-b4 instance.";

             leaf id AFTR YANG Module

<CODE BEGINS> file "ietf-dslite-aftr@2017-07-27.yang"

module ietf-dslite-aftr {
                type uint32;
                description
                  "dslite-b4 instance identifier.";

             }

             leaf name
    namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-aftr";
    prefix dslite-aftr;

    import ietf-inet-types {
                type string;
                description
                  "A name associated with the dslite-b4 instance."; prefix inet; }

            leaf aftr-ipv6-addr

    import ietf-nat {
                type inet:ipv6-address;
                mandatory true;
                description
                   "The AFTR's IPv6 address.";
       prefix nat;
     }

      leaf ipv4-address {
          type inet:ipv4-address;
          default "192.0.0.2";

    organization "Softwire Working Group";
    contact
     "Mohamed Boucadair <mohamed.boucadair@orange.com>
      Christian Jacquenet <christian.jacquenet@orange.com>
      Senthil Sivakumar <ssenthil@cisco.com>";

   description
            "IPv4 address of the DS-Lite B4.
            192.0.0.0/29
      "This module is reserved for the B4 element
            [RFC6333].
            This address can be used to report ICMP
            problems and will appear in traceroute
            outputs.";
      }

      leaf tunnel-mtu {
          type uint16;
          description
              "Configures a tunnel MTU.
              [RFC6908] specifies that since
              fragmentation and reassembly is not
              optimal, the operator should do
              everything possible to eliminate
              the need YANG module for it.  If the operator uses
              simple IPv4-in-IPv6 softwire, it is
              recommended that the MTU size of the IPv6
              network between the B4 and the DS-Lite AFTR
              accounts for the additional overhead
              (40 bytes).";
      }

      leaf v6-v4-dscp-preservation {
          type boolean;
          mandatory true;
          description
           "Copies
      implementations.

      Copyright (c) 2017 IETF Trust and the DSCP value from persons identified as
      authors of the IPv6 header code.  All rights reserved.

      Redistribution and vice versa.
           According to Section 2.10 of [RFC6908],
           operators should use this model
           by provisioning the network such that
           the AFTR copies the DSCP value in the IPv4
           header source and binary forms, with or
      without modification, is permitted pursuant to, and subject
      to the Traffic Class field license terms contained in, the Simplified BSD License
      set forth in Section 4.c of the IPv6 header, after 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 encapsulation RFC itself for the downstream traffic.";
      }
      }
    }
   }
  }

  /*
    * DS-Lite State
    */

  container dslite-state {

      description
         "dslite-aftr and b4 state.";

  /*
   * DS-Lite AFTR State
   */

  container dslite-aftr-state {

      if-feature aftr;

      config false;

      description
         "dslite-aftr";

      container dslite-aftr-instances {
          description
              "dslite-aftr instances";

          list dslite-aftr-instance {
              key "id";

              description
               "dslite-aftr instance";

              leaf id full legal notices.";

    revision 2017-07-27 {
                  type int32;
      description
                    "The identifier of "Redesign the dslite-aftr instance.";
              }

              leaf name {
                  type string;
                  description
                   "The name module as an augment of the dslite-aftr instance.";
              }

              container aftr-capabilities {
                 description
                    "AFTR capabilities";

                 leaf eim-support {
                        type boolean;
                        description
                          "Indicates whether EIM is enabled.";
                 }

                 leaf eif-support {
                        type boolean;
                        description
                          "Indicates whether EIF is enabled.";
                 }

                 leaf edm-support {
                        type boolean;
                        description
                          "Indicates whether EDM is enabled.";
                 }

                 leaf edf-support {
                        type boolean;
                        description
                          "Indicates whether EDF is enabled.";
                 }

                 leaf adm-support {
                        type boolean;
                        description
                          "Indicates whether ADM is enabled."; NAT YANG module.";
       reference "-ietf-04";
    }

                 leaf adf-support

    revision 2017-07-03 {
                        type boolean;
      description
                          "Indicates whether ADF is enabled."; "Fix some minor points.";
       reference "-ietf-03";
    }

                 leaf pcp-support

    revision 2017-01-03 {
                        type boolean;
      description
                          "Indicates whether "Fixed a PCP server is enabled."; compilation error:
        https://github.com/mbj4668/pyang/issues/296.";
       reference "-ietf-02";
    }

                 leaf subscriber-mask-support{
                     type boolean;

    revision 2016-11-14 {
      description
                       "Indicates whether "Integrates the subscriber-mask feature
                        is supported."; comments from Ian:
      add B4 module, add an MSS leaf, add more details about
      logging protocols, and other edits.";
       reference "-ietf-01";
    }

                 leaf port-set-support

    revision 2016-07-27 {
                    type boolean;
      description
                     "Indicates whether port set assignment is
                     supported."; "-00 IETF version.";
       reference "-ietf-00";
    }

                 leaf self-state-migration-support

    revision 2016-06-13 {
                    type boolean;
      description
                     "Indicates whether mappings migration
                     to the new IPv6 address used by "Update the B4 is
                     supported [RFC7785]."; module.";
       reference "-04";
    }

                 leaf mss-clamping-support

    revision 2015-12-16 {
                        type boolean;
      description
                          "Indicates whether the MSS clamping
                          feature is supported."; "Fix an error.";
       reference "-03";
    }

                 leaf port-randomization-support

    revision 2015-09-01 {
                    type boolean;
      description
                     "Indicates whether "Add port randomization is
                     supported."; threshold notifications.";
       reference "-02";
    }

                 leaf port-preservation-support

    revision 2015-08-31 {
                    type boolean;
      description
                     "Indicates whether port preservation
                     is supported."; "Fix a timeout issue.";
       reference "-01";
    }

                 leaf port-parity-preservation-support

    revision 2015-08-17 {
                    type boolean;
      description
                     "Indicates whether port parity preservation is
                      supported."; "First spec.";
       reference "-00";
    }

                 list transport-proto-capabilities

// Augment NAT module with AFTR parameters

augment "/nat:nat-module/nat:nat-instances/nat:nat-instance" {
                   key "transport-protocol-id";
   description
                     "A set of supported transport protocols.";
        "Augments NAT module with AFTR parameters.";

   leaf transport-protocol-id ipv6-address {
           type uint8; inet:ipv6-address;
           description
                        "ID
             "IPv6 address of the transport protocol.";
                   } dslite-aftr.";

           reference
              "RFC 6333.";
        }

    leaf v6-v4-dscp-preservation-support ipv4-address {
        type boolean; inet:ipv4-address;
        default "192.0.0.1";
        description
                          "Copy
          "IPv4 address of the DSCP value from DS-Lite AFTR.
          192.0.0.1 is reserved for the IPv6 header AFTR element.
          This address can be used to report ICMP
          problems and vice versa."; will appear in traceroute
          outputs.";

        reference
          "RFC 6333.";
    }

    leaf logging-support tunnel-mtu {
        type boolean; uint16;
        description
                       "Indicates whether
            "Configures a logging feature tunnel MTU.
            [RFC6908] specifies that since
            fragmentation and reassembly is
                       supported.";
                 }

            leaf ftp-alg-support {
                 type boolean;
                 description
                    "Indicates whether FTP ALG not
            optimal, the operator should do
            everything possible to eliminate
            the need for it.  If the operator uses
            simple IPv4-in-IPv6 softwire, it is supported.";
            recommended that the MTU size of the IPv6
            network between the B4 and the AFTR
            accounts for the additional overhead
            (40 bytes).";

        reference
          "RFC 6908.";
    }

    leaf tftp-support subscriber-mask {
        type boolean;
                 description
                    "Indicates whether TFTP ALG is supported.";

            }

            leaf sip-alg-support uint8 {
                 type boolean;
                 description
                    "Indicates whether SIP ALG is supported.";
            range "0 .. 128";
            }

            leaf rtsp-alg-support {
                 type boolean;
        default "56";
        description
                    "Indicates whether RTSP ALG
            "The subscriber-mask is an integer that indicates
             the length of significant bits to be applied on
             the source IPv6 address (internal side) to
             unambiguously identify a CPE.

             Subscriber-mask is a system-wide configuration
             parameter that is used to enforce generic
             per-subscriber policies (e.g., port-quota).

             The enforcement of these generic policies does not
             require the configuration of every subscriber's prefix.

             Example: suppose the 2001:db8:100:100::/56 prefix is
             assigned to a DS-Lite enabled CPE. Suppose also that the
             2001:db8:100:100::1 is the IPv6 address used by the
             B4 that resides in that CPE. When the AFTR
             receives a packet from this client,
             it applies the subscriber-mask (e.g., 56) on
             the source IPv6 address to compute the associated prefix
             for this client (that is supported."; 2001:db8:100:100::/56).  Then,
             the AFTR enforces policies based on that prefix
             (2001:db8:100:100::/56), not on the exact
             source IPv6 address";

        reference
          "RFC 7785.";
    }

    leaf h323-alg-support state-migrate {
        type boolean;
        default true;
        description
                    "Indicates whether H323 ALG
            "State migration is supported.";
            }
               }

              container aftr-current-config {
                 description
                      "current config";

                 uses aftr-parameters;
              }

              container mapping-table {
                  description
                      "Mapping table";
                  list mapping-entry {
                      key "index";
                      description
                          "mapping entry";
                      uses mapping-entry;
                      } enabled by default.";

        reference
          "RFC 7785.";
    }

              container statistics {
                  description
                       "traffic statistics";

                  container traffic-statistics {
                              description
                                "Generic traffic statistics.";

    leaf sent-packet max-softwire-per-subscriber {
        type yang:zero-based-counter64; uint8;
        default 1;
        description
                                  "Number
         "Configures the maximum softwire per subscriber
         feature.

        A subscriber is uniquely identified by means
        of packets sent.";
                              }

                              leaf sent-byte {
                                type yang:zero-based-counter64;
                                description
                                  "Counter for sent traffic in bytes.";
                              }

                              leaf rcvd-packet {
                                type yang:zero-based-counter64;
                                description
                                   "Number subscriber-mask.

        This policy aims to prevent a misbehaving
        subscriber from mounting several DS-Lite
        softwires that would consume additional AFTR
        resources (e.g., get more external ports if
        the quota were enforced on a per-softwire basis,
        consume extra processing due to a large number
        of active softwires).";

        reference
          "Section 4 of received packets."; RFC 7785.";
    }

                              leaf rcvd-byte

    container mss-clamping {
                                type yang:zero-based-counter64;
        description
                                 "Counter for received traffic
                                 in bytes.";
                              }
          "MSS rewriting configuration.";

        leaf dropped-packet mss-clamping-enable {
           type yang:zero-based-counter64; boolean;
           description
                                 "Number of dropped packets.";
             "Enable/disable MSS rewriting feature.";
        }

        leaf dropped-byte mss-value {
          type yang:zero-based-counter64; uint16;
          units "octets";
          description
                                  "Counter
            "Sets the MSS value to be used for dropped traffic in
                                  bytes.";
             MSS rewriting.";
        }
     }

                           container mapping-table-stats {
                             description
                              "Mapping table statistics.";

    leaf current-mt-size v6-v4-dscp-preservation {
        type yang:zero-based-counter64; boolean;
        description
                            "Size of
         "Copies the mapping table.";
                          }
                          leaf max-mt-size {
                            type uint32;
                                 description
                                   "Maximum configured size of DSCP value from the
                                   mapping table.";
                             }

                            leaf total-tcp-mappings {
                                 type uint32;
                                 description
                                  "Total number IPv6 header
         and vice versa.
         According to Section 2.10 of TCP Mappings present
                                  at [RFC6908],
         operators should use this model
         by provisioning the time.";
                            }
                            leaf total-udp-mappings {
                                 type uint32;
                                 description
                                  "Total number of UDP Mappings present
                                  at network such that
         the AFTR copies the DSCP value in the IPv4
         header to the Traffic Class field in
         the IPv6 header, after the time."; encapsulation
         for the downstream traffic.";

        reference
          "Section 2.10 of RFC 6908.";
    }

                            leaf total-icmp-mappings {
                                 type uint32;
}

// Augment NAT mapping entry:  Extended NAT44 mapping Entry

augment "/nat:nat-module/nat:nat-instances/nat:nat-instance/nat:mapping-table/nat:mapping-entry"{
   description
                                  "Total number of ICMP Mappings present
                                  at
     "Augments the time.";
                            }
                        }
                      } NAT mapping table with DS-Lite specifics.";

    leaf available-capacity-client b4-ip-address {
        type percent; inet:ipv6-address;
        description
                            "Ratio of available capacity in
            "Corresponds to the IPv6 address
            used by the
                            customer-facing interfaces."; B4 element.";

        reference
          "RFC 6333.";
     }

   leaf available-capacity-ext v6-dscp {
        type percent; uint8;
        description
                            "Ratio of available capacity in
          "DSCP value used at the
                            Internet-facing interfaces."; softwire level
          (i.e., IPv6 header).";
   }

   leaf address-pool-in-use internal-v4-dscp {
        type percent; uint8;
        description
                            "Ratio
          "DSCP value of the shared address pool."; encapsulated IPv4 packet.";
   }

   leaf port-in-use external-v4-dscp {
        type percent; uint8;
        description
                            "Ratio
          "DSCP value of the port usage.";
                      } translated IPv4 packet
           as marked by the AFTR.";
   }
 }
}

  /*
   *
<CODE ENDS>

4.  DS-Lite B4 State
   */

  container dslite-b4-state {

      if-feature b4;

      config false;

      description
         "dslite-b4";

      container dslite-b4-instances {
          description
              "dslite-b4 instances";

          list dslite-b4-instance YANG Module

   <CODE BEGINS> file "ietf-dslite-b4@2017-07-27.yang"

   module ietf-dslite-b4 {
              key "id";

              description
               "dslite-b4 instance";

              leaf id
       namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-b4";
       prefix dslite-b4;

       import ietf-inet-types {
                  type int32; prefix inet; }

       organization "Softwire Working Group";
       contact
        "Mohamed Boucadair <mohamed.boucadair@orange.com>
         Christian Jacquenet <christian.jacquenet@orange.com>
         Senthil Sivakumar <ssenthil@cisco.com>";

      description
                    "The identifier
         "This module is a YANG module for DS-Lite B4 implementations.

         Copyright (c) 2017 IETF Trust and the persons identified as
         authors of the dslite-b4 instance.";
              }

              leaf name {
                  type string;
                  description
                   "The name 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 dslite-b4 instance.";
              }

              // 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 2017-07-27 {
         description "Separate B4 Capabilities from AFTR.";
          reference "-ietf-04";
       }

   container b4-capabilities dslite-b4 {

       description
                      "B4 capabilities";
        "dslite-b4";

       leaf ipv4-address-modify enable {
           type boolean;
           description
                          "Indicates whether it is possible
                           to configure an IPv4 address
                           for the B4 element.";
            "Enable/disable dslite-b4 function.";
       }

                  leaf tunnel-mtu-support

       container dslite-b4-instances {
                      type boolean;
          description
                          "Indicates whether it is possible to
                      configure a tunnel MTU.
                      ";
                  }
            "dslite-b4 instances";

           list dslite-b4-instance {
               key "id";
                 description
                   "a dslite-b4 instance.";

              leaf v6-v4-dscp-preservation-support id {
                 type boolean;
                      mandatory true; uint32;
                 description
                          "Indicates whether it supports
                      DSCP preservation.
                      ";
                  }
                   "dslite-b4 instance identifier.";
              }

           // B4 State

            container b4-state {
                description
                    "B4 capabilities";

              leaf status name {
                 type boolean; string;
                 description
                        "Indicates whether
                   "A name associated with the instance is
                    enabled or disabled.
                    "; dslite-b4 instance.";
              }

             leaf aftr-ipv6-addr {
                 type inet:ipv6-address;
                 mandatory true;
                 description
                    "The AFTR's IPv6 address.";

                 reference
                    "RFC 6333.";
              }

       leaf ipv4-address-configured ipv4-address {
           type inet:ipv4-address;
           default "192.0.0.2";
           description
                        "The B4's IPv4 address.";
             "IPv4 address of the DS-Lite B4.
             192.0.0.0/29 is reserved for the B4 element
             [RFC6333].
             This address can be used to report ICMP
             problems and will appear in traceroute
             outputs.";

           reference
                "RFC 6333.";
       }

       leaf v6-v4-dscp-preservation-enabled tunnel-mtu {
           type boolean; uint16;
           description
                        "Indicates whether this feature
               "Configures a tunnel MTU.
               [RFC6908] specifies that since
               fragmentation and reassembly is
                    enabled/disabled.
                    ";
                } not
               optimal, the operator should do
               everything possible to eliminate
               the need for it.  If the operator uses
               simple IPv4-in-IPv6 softwire, it is
               recommended that the MTU size of the IPv6
               network between the B4 and the AFTR
               accounts for the additional overhead
               (40 bytes).";

            reference
                "RFC 6908.";
       }

       leaf v6-v4-dscp-preservation {
           type boolean;
           mandatory true;
           description
            "Copies the DSCP value from the IPv6 header
            and vice versa.
            According to Section 2.10 of [RFC6908],
            operators should use this model
            by provisioning the network such that
            the AFTR copies the DSCP value in the IPv4
            header to the Traffic Class field in
            the IPv6 header, after the encapsulation
            for the downstream traffic.";
       }
       }
     }
    }
   }
   <CODE ENDS>

4.

5.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241].  The lowest NETCONF layer is the
   secure transport layer and the support of SSH is mandatory to
   implement secure transport [RFC6242].  The NETCONF access control
   model [RFC6536] provides means to restrict access for particular
   NETCONF users to a pre-configured subset of all available NETCONF
   protocol operations and contents.

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

5.

6.  IANA Considerations

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

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

            URI: urn:ietf:params:xml:ns:yang:ietf-dslite-b4
            Registrant Contact: The IESG.
            XML: N/A; the requested URI is an XML namespace.

   This document requests IANA to register the following YANG module modules in
   the "YANG Module Names" registry [RFC6020].

            name: ietf-dslite ietf-dslite-aftr
            namespace: urn:ietf:params:xml:ns:yang:ietf-dslite urn:ietf:params:xml:ns:yang:ietf-dslite-aftr
            prefix: dslite dslite-aftr
            reference: RFC XXXX

6.

            name: ietf-dslite-b4
            namespace: urn:ietf:params:xml:ns:yang:ietf-dslite-b4
            prefix: dslite-b4
            reference: RFC XXXX

7.  Acknowledgements

   Thanks to Q.  Wu for identifying a compiling error.

   Many thanks to Ian Farrer for the review and comments.

7.

8.  References

7.1.

8.1.  Normative references

   [I-D.sivakumar-yang-nat]
              Sivakumar, S., Boucadair, M., and S. Vinapamula, "YANG
              Data Model for Network Address Translation (NAT)", draft-
              sivakumar-yang-nat-07 (work in progress), July 2017.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <http://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,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6242>.

   [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,
              <http://www.rfc-editor.org/info/rfc6333>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <http://www.rfc-editor.org/info/rfc6536>.

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

7.2.

8.2.  Informative references

   [I-D.boucadair-pcp-yang]
              Boucadair, M., Jacquenet, C., Sivakumar, S., and S.
              Vinapamula, "YANG Data Models for the Port Control
              Protocol (PCP)", draft-boucadair-pcp-yang-04 (work in
              progress), May 2017.

   [RFC4787]  Audet, F., Ed. and C. Jennings, "Network Address
              Translation (NAT) Behavioral Requirements for Unicast
              UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
              2007, <http://www.rfc-editor.org/info/rfc4787>.

   [RFC5382]  Guha, S., Ed., Biswas, K., Ford, B., Sivakumar, S., and P.
              Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
              RFC 5382, DOI 10.17487/RFC5382, October 2008,
              <http://www.rfc-editor.org/info/rfc5382>.

   [RFC5508]  Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT
              Behavioral Requirements for ICMP", BCP 148, RFC 5508,
              DOI 10.17487/RFC5508, April 2009,
              <http://www.rfc-editor.org/info/rfc5508>.

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

   [RFC6888]  Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
              A., and H. Ashida, "Common Requirements for Carrier-Grade
              NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
              April 2013, <http://www.rfc-editor.org/info/rfc6888>.

   [RFC6908]  Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M.
              Boucadair, "Deployment Considerations for Dual-Stack
              Lite", RFC 6908, DOI 10.17487/RFC6908, March 2013,
              <http://www.rfc-editor.org/info/rfc6908>.

   [RFC7753]  Sun, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, T.,
              and S. Perreault, "Port Control Protocol (PCP) Extension
              for Port-Set Allocation", RFC 7753, DOI 10.17487/RFC7753,
              February 2016, <http://www.rfc-editor.org/info/rfc7753>.

   [RFC7785]  Vinapamula, S. and M. Boucadair, "Recommendations for
              Prefix Binding in the Context of Softwire Dual-Stack
              Lite", RFC 7785, DOI 10.17487/RFC7785, February 2016,
              <http://www.rfc-editor.org/info/rfc7785>.

   [RFC7857]  Penno, R., Perreault, S., Boucadair, M., Ed., Sivakumar,
              S., and K. Naito, "Updates to Network Address Translation
              (NAT) Behavioral Requirements", BCP 127, RFC 7857,
              DOI 10.17487/RFC7857, April 2016,
              <http://www.rfc-editor.org/info/rfc7857>.

Authors' Addresses

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   EMail: mohamed.boucadair@orange.com

   Christian Jacquenet
   Orange
   Rennes  35000
   France

   EMail: christian.jacquenet@orange.com

   Senthil Sivakumar
   Cisco Systems
   7100-8 Kit Creek Road
   Research Triangle Park, North Carolina  27709
   USA

   Phone: +1 919 392 5158
   EMail: ssenthil@cisco.com