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For this RFC, original HTML is available from the RFC-Editor: RFC8658

PROPOSED STANDARD

Internet Engineering Task Force (IETF)                     S. Jiang, Ed.
Request for Comments: 8658                                        Huawei
Category: Standards Track                                     Y. Fu, Ed.
ISSN: 2070-1721                                                    CNNIC
                                                                  C. Xie
                                                           China Telecom
                                                                   T. Li
                                                     Tsinghua University
                                                       M. Boucadair, Ed.
                                                                  Orange
                                                           November 2019


           RADIUS Attributes for Softwire Mechanisms Based on
                        Address plus Port (A+P)

Abstract

   IPv4-over-IPv6 transition mechanisms provide IPv4 connectivity
   services over IPv6 native networks during the IPv4/IPv6 coexistence
   period.  DHCPv6 options have been defined to configure clients for
   Lightweight 4over6, Mapping of Address and Port with Encapsulation
   (MAP-E), Mapping of Address and Port using Translation (MAP-T)
   unicast softwire mechanisms, and multicast softwires.  However, in
   many networks, configuration information is stored in an
   Authentication, Authorization, and Accounting (AAA) server, which
   utilizes the Remote Authentication Dial In User Service (RADIUS)
   protocol to provide centralized management for users.  When a new
   transition mechanism is developed, new RADIUS attributes need to be
   defined correspondingly.

   This document defines new RADIUS attributes to carry softwire
   configuration parameters based on Address plus Port from a AAA server
   to a Broadband Network Gateway.  Both unicast and multicast
   attributes are covered.

Status of This Memo

   This is an Internet Standards Track document.

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

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8658.

Copyright Notice

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

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

Table of Contents

   1.  Introduction
   2.  Terminology
   3.  New RADIUS Attributes
     3.1.  Softwire46-Configuration Attribute
       3.1.1.  Softwire46 Attributes
         3.1.1.1.  Softwire46-MAP-E Attribute
         3.1.1.2.  Softwire46-MAP-T Attribute
         3.1.1.3.  Softwire46-Lightweight-4over6 Attribute
       3.1.2.  Softwire46 Sub-attributes
       3.1.3.  Specification of the Softwire46 Sub-attributes
         3.1.3.1.  Softwire46-Rule Attribute
         3.1.3.2.  Softwire46-BR Attribute
         3.1.3.3.  Softwire46-DMR Attribute
         3.1.3.4.  Softwire46-V4V6Bind Attribute
         3.1.3.5.  Softwire46-PORTPARAMS Attribute
       3.1.4.  Sub-attributes for Softwire46-Rule
         3.1.4.1.  Rule-IPv6-Prefix Attribute
         3.1.4.2.  Rule-IPv4-Prefix Attribute
         3.1.4.3.  EA-Length Attribute
       3.1.5.  Attributes for Softwire46-v4v6Bind
         3.1.5.1.  IPv4-Address Attribute
         3.1.5.2.  Bind-IPv6-Prefix Attribute
       3.1.6.  Attributes for Softwire46-PORTPARAMS
         3.1.6.1.  PSID-Offset Attribute
         3.1.6.2.  PSID-Len Attribute
         3.1.6.3.  PSID Attribute
     3.2.  Softwire46-Priority Attribute
       3.2.1.  Softwire46-Option-Code
     3.3.  Softwire46-Multicast Attribute
       3.3.1.  ASM-Prefix64 Attribute
       3.3.2.  SSM-Prefix64 Attribute
       3.3.3.  U-Prefix64 Attribute
   4.  A Sample Configuration Process with RADIUS
   5.  Table of Attributes
   6.  Security Considerations
   7.  IANA Considerations
     7.1.  New RADIUS Attributes
     7.2.  RADIUS Softwire46 Configuration and Multicast
           Attributes
     7.3.  Softwire46 Mechanisms and Their Identifying Option
           Codes
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  DHCPv6 to RADIUS Field Mappings
     A.1.  OPTION_S46_RULE (89) to Softwire46-Rule Sub-TLV Field
           Mappings
     A.2.  OPTION_S46_BR (90) to Softwire46-BR Field Mappings
     A.3.  OPTION_S46_DMR (91) to Softwire46-DMR
     A.4.  OPTION_S46_V4V6BIND (92) to Softwire46-V4V6Bind
     A.5.  OPTION_S46_PORTPARAMS (93) to Softwire46-PORTPARAMS
           Field Mappings
     A.6.  OPTION_S46_PRIORITY (111) to Softwire46-PORTPARAMS
           Field Mappings
     A.7.  OPTION_V6_PREFIX64 (113) to Softwire46-Multicast
           Attribute Field Mappings
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   Providers have started deploying and transitioning to IPv6.  Several
   IPv4 service continuity mechanisms based on Address plus Port (A+P)
   [RFC6346] have been proposed for providing unicast IPv4-over-
   IPv6-only infrastructure, such as Mapping of Address and Port with
   Encapsulation (MAP-E) [RFC7597], Mapping of Address and Port using
   Translation (MAP-T) [RFC7599], and Lightweight 4over6 [RFC7596].
   Also, [RFC8114] specifies a generic solution for the delivery of IPv4
   multicast services to IPv4 clients over an IPv6 multicast network.
   For each of these mechanisms, DHCPv6 options have been specified for
   client configuration.

   In many networks, user configuration information is stored in an
   Authentication, Authorization, and Accounting (AAA) server.  AAA
   servers generally communicate using the Remote Authentication Dial In
   User Service (RADIUS) [RFC2865] protocol.  In a fixed broadband
   network, a Broadband Network Gateway (BNG) acts as the access gateway
   for users.  That is, the BNG acts as both a AAA client to the AAA
   server and a DHCPv6 server for DHCPv6 messages sent by clients.
   Throughout this document, the term "BNG" describes a device
   implementing both the AAA client and DHCPv6 server functions.

   Since IPv4-in-IPv6 softwire configuration information is stored in a
   AAA server and user configuration information is mainly transmitted
   through DHCPv6 between the BNGs and Customer Premises Equipment (CEs,
   a.k.a., CPE), new RADIUS attributes are needed to propagate the
   information from the AAA servers to BNGs so that they can be provided
   to CEs using the existing DHCPv6 options.

   The RADIUS attributes defined in this document provide the
   configuration to populate the corresponding DHCPv6 options for
   unicast and multicast softwire configurations, specifically:

   *  "Mapping of Address and Port with Encapsulation (MAP-E)" [RFC7597]
      (DHCPv6 options defined in [RFC7598]).

   *  "Mapping of Address and Port using Translation (MAP-T)" [RFC7599]
      (DHCPv6 options defined in [RFC7598]).

   *  "Lightweight 4over6: An Extension to the Dual-Stack Lite
      Architecture" [RFC7596] (DHCPv6 options defined in [RFC7598]).

   *  "Unified IPv4-in-IPv6 Softwire Customer Premises Equipment (CPE):
      A DHCPv6-Based Prioritization Mechanism" [RFC8026].

   *  "Delivery of IPv4 Multicast Services to IPv4 Clients over an IPv6
      Multicast Network" [RFC8114] (DHCPv6 options defined in
      [RFC8115]).

   The contents of the attributes defined in this document have a 1:1
   mapping into the fields of the various DHCPv6 options in [RFC7598],
   [RFC8026], and [RFC8115].  Table 1 shows how the DHCPv6 options map
   to the corresponding RADIUS attribute.  For detailed mappings between
   each DHCPv6 option field and the corresponding RADIUS attribute or
   field, see Appendix A.

          +----------------------------+-----------------------+
          | DHCPv6 Option              | RADIUS Attribute      |
          +============================+=======================+
          | OPTION_S46_RULE (89)       | Softwire46-Rule       |
          +----------------------------+-----------------------+
          | OPTION_S46_BR (90)         | Softwire46-BR         |
          +----------------------------+-----------------------+
          | OPTION_S46_DMR (91)        | Softwire46-DMR        |
          +----------------------------+-----------------------+
          | OPTION_S46_V4V6BIND (92)   | Softwire46-V4V6Bind   |
          +----------------------------+-----------------------+
          | OPTION_S46_PORTPARAMS (93) | Softwire46-PORTPARAMS |
          +----------------------------+-----------------------+
          | OPTION_S46_PRIORITY (111)  | Softwire46-Priority   |
          +----------------------------+-----------------------+
          | OPTION_V6_PREFIX64 (113)   | Softwire46-Multicast  |
          +----------------------------+-----------------------+

               Table 1: Mapping between DHCPv6 Options and
                            RADIUS Attributes

   A RADIUS attribute for Dual-Stack Lite [RFC6333] is defined in
   [RFC6519].

   This document targets deployments where a trusted relationship is in
   place between the RADIUS client and server.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The reader should be familiar with the concepts and terms defined in
   [RFC7596], [RFC7597], [RFC7599], and [RFC8026].

   The terms "multicast Basic Bridging BroadBand" element (mB4) and
   "multicast Address Family Transition Router" element (mAFTR) are
   defined in [RFC8114].

   Softwire46 (S46) is used throughout to denote any of the IPv4-in-IPv6
   softwire mechanisms listed above.  Additionally, the following
   abbreviations are used within the document:

   BNG:      Broadband Network Gateway

   BR:       Border Relay

   CE:       Customer Edge

   CoA:      Change-of-Authorization

   DMR:      Default Mapping Rule

   EA:       Embedded Address

   lwAFTR:   Lightweight Address Family Transition Router

   MAP-E:    Mapping of Address and Port with Encapsulation

   MAP-T:    Mapping of Address and Port using Translation

   PSID:     Port Set Identifier

   TLV:      Type, Length, Value

3.  New RADIUS Attributes

   This section defines the following attributes:

   1.  Softwire46-Configuration Attribute (Section 3.1):

       This attribute carries the configuration information for MAP-E,
       MAP-T, and Lightweight 4over6.  The configuration information for
       each Softwire46 mechanism is carried in the corresponding
       Softwire46 attributes.  Different attributes are required for
       each Softwire46 mechanism.

   2.  Softwire46-Priority Attribute (Section 3.2):

       Depending on the deployment scenario, a client may support
       several different Softwire46 mechanisms.  Therefore, a client may
       request configuration for more than one Softwire46 mechanism at a
       time.  The Softwire46-Priority Attribute contains information
       allowing the client to prioritize which mechanism to use,
       corresponding to OPTION_S46_PRIORITY defined in [RFC8026].

   3.  Softwire46-Multicast Attribute (Section 3.3):

       This attribute conveys the IPv6 prefixes to be used in [RFC8114]
       to synthesize IPv4-embedded IPv6 addresses.  The BNG uses the
       IPv6 prefixes returned in the RADIUS Softwire46-Multicast
       Attribute to populate the DHCPv6 PREFIX64 Option [RFC8115].

   All of these attributes are allocated from the RADIUS "Extended Type"
   code space per [RFC6929].

   All of these attribute designs follow [RFC6158] and [RFC6929].

   This document adheres to the guidance in [RFC8044] for defining new
   RADIUS attributes.

3.1.  Softwire46-Configuration Attribute

   This attribute is of type "tlv", as defined in "Remote Authentication
   Dial-In User Service (RADIUS) Protocol Extensions" [RFC6929].  It
   contains some sub-attributes, with the following requirements:

   *  The Softwire46-Configuration Attribute MUST contain one or more of
      the following attributes: Softwire46-MAP-E, Softwire46-MAP-T, and/
      or Softwire46-Lightweight-4over6.

   *  The Softwire46-Configuration Attribute conveys the configuration
      information for MAP-E, MAP-T, or Lightweight 4over6.  The BNG
      SHALL use the configuration information returned in the RADIUS
      attribute to populate the DHCPv6 Softwire46 container option(s)
      defined in Section 5 of [RFC7598].

   *  The Softwire46-Configuration Attribute MAY appear in an Access-
      Accept packet.  It MAY also appear in an Access-Request packet to
      indicate a preferred Softwire46 configuration.  However, the
      server is not required to honor such a preference.

   *  The Softwire46-Configuration Attribute MAY appear in a CoA-Request
      packet.

   *  The Softwire46-Configuration Attribute MAY appear in an
      Accounting-Request packet.

   *  The Softwire46-Configuration Attribute MUST NOT appear in any
      other RADIUS packet.

   The Softwire46-Configuration Attribute is structured as follows:

   Type
      241

   Length
      Indicates the total length, in bytes, of all fields of this
      attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded attributes.

   Extended-Type
      9

   Value
      Contains one or more of the following attributes.  Each attribute
      type may appear once at most:

      Softwire46-MAP-E
         For configuring MAP-E clients.  For the construction of this
         attribute, refer to Section 3.1.1.1.

      Softwire46-MAP-T
         For configuring MAP-T clients.  For the construction of this
         attribute, refer to Section 3.1.1.2.

      Softwire46-Lightweight-4over6
         For configuring Lightweight 4over6 clients.  For the
         construction of this attribute, refer to Section 3.1.1.3.

   The Softwire46-Configuration Attribute is associated with the
   following identifier: 241.9.

3.1.1.  Softwire46 Attributes

   The Softwire46 attributes can only be encapsulated in the
   Softwire46-Configuration Attribute.  Depending on the deployment
   scenario, a client might request more than one transition mechanism
   at a time.  There MUST be at least one Softwire46 attribute
   encapsulated in one Softwire46-Configuration Attribute.  There MUST
   be at most one instance of each type of Softwire46 attribute
   encapsulated in one Softwire46-Configuration Attribute.

   There are three types of Softwire46 attributes, namely:

   1.  Softwire46-MAP-E (Section 3.1.1.1)

   2.  Softwire46-MAP-T (Section 3.1.1.2)

   3.  Softwire46-Lightweight 4over6 (Section 3.1.1.3)

   Each type of Softwire46 attribute contains a number of sub-
   attributes, defined in Section 3.1.3.  The hierarchy of the
   Softwire46 attributes is shown in Figure 1.  Section 3.1.2 describes
   which sub-attributes are mandatory, optional, or not permitted for
   each defined Softwire46 attribute.

                                               /1.Rule-IPv6-Prefix
   S                      /                    |
   o  /                  | 1.Softwire46-Rule --+ 2.Rule-IPv4-Prefix
   f | Softwire46-MAP-E--+                     |
   t |                   | 2.Softwire46-BR     | 3.EA-Length
   w |                   |                      \
   i |                   |                               /1.PSID-Offset
   r |                   |                              |
   e |                   | 3.Softwire46-PORTPARAMS -----+ 2.PSID-Len
   4 |                    \                             |
   6 |                                                  | 3.PSID
   - |                                                   \
   C |
   o |                                          /1.Rule-IPv6-Prefix
   n |                    /                    |
   f |                   | 1.Softwire46-Rule---+ 2.Rule-IPv4-Prefix
   i | Softwire46-MAP-T--+                     |
   g |                   | 2.Softwire46-DMR    | 3.EA-Length
   u |                   |                      \
   r |                   |                               /1.PSID-Offset
   a |                   |                              |
   t |                   | 3.Softwire46-PORTPARAMS------+ 2.PSID-Len
   i |                    \                             |
   o |                                                  | 3.PSID
   n |                                                   \
     |
   A |                                              /1.IPv4-Address
   t |                    /                        |
   t |                   | 1.Softwire46-V4V6Bind --+ 2.Bind-IPv6-Prefix
   r | Softwire46-       |                          \
   i | Lightweight-4over6+ 2.Softwire46-BR               /1.PSID-Offset
   b  \                  |                              |
   u                     | 3.Softwire46-PORTPARAMS  ----+ 2.PSID-Len
   t                      \                             |
   e                                                    | 3.PSID
                                                         \

                  Figure 1: Softwire46 Attribute Hierarchy

3.1.1.1.  Softwire46-MAP-E Attribute

   The Softwire46-MAP-E attribute is designed to carry the configuration
   information for MAP-E.  The structure of Softwire46-MAP-E is shown
   below:

   TLV-Type
      1

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   TLV-Value
      Contains a set of sub-attributes, with the following requirements:

      It MUST contain Softwire46-Rule, defined in Section 3.1.3.1.

      It MUST contain Softwire46-BR, defined in Section 3.1.3.2.

      It MAY contain Softwire46-PORTPARAMS, defined in Section 3.1.3.5.

3.1.1.2.  Softwire46-MAP-T Attribute

   The Softwire46-MAP-T attribute is designed to carry the configuration
   information for MAP-T.  The structure of Softwire46-MAP-T is shown
   below:

   TLV-Type
      2

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   TLV-Value
      Contains a set of sub-attributes, with the following requirements:

      It MUST contain Softwire46-Rule, defined in Section 3.1.3.1.

      It MUST contain Softwire46-DMR, defined in Section 3.1.3.3.

      It MAY contain Softwire46-PORTPARAMS, defined in Section 3.1.3.5.

3.1.1.3.  Softwire46-Lightweight-4over6 Attribute

   The Softwire46-Lightweight-4over6 attribute is designed to carry the
   configuration information for Lightweight 4over6.  The structure of
   Softwire46-Lightweight-4over6 is shown below:

   TLV-Type
      3

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   TLV-Value
      Contains a set of sub-attributes as follows:

      It MUST contain Softwire46-BR, defined in Section 3.1.3.2.

      It MUST contain Softwire46-V4V6Bind, defined in Section 3.1.3.4.

      It MAY contain Softwire46-PORTPARAMS, defined in Section 3.1.3.5.

3.1.2.  Softwire46 Sub-attributes

   Table 2 shows which encapsulated sub-attributes are mandatory,
   optional, or not permitted for each defined Softwire46 attribute.

      +-----------------------+-------+-------+--------------------+
      | Sub-attributes        | MAP-E | MAP-T | Lightweight 4over6 |
      +=======================+=======+=======+====================+
      | Softwire46-BR         | 1+    | 0     | 1+                 |
      +-----------------------+-------+-------+--------------------+
      | Softwire46-Rule       | 1     | 1     | 0                  |
      +-----------------------+-------+-------+--------------------+
      | Softwire46-DMR        | 0     | 1     | 0                  |
      +-----------------------+-------+-------+--------------------+
      | Softwire46-V4V6Bind   | 0     | 0     | 1                  |
      +-----------------------+-------+-------+--------------------+
      | Softwire46-PORTPARAMS | 0-1   | 0-1   | 0-1                |
      +-----------------------+-------+-------+--------------------+

                    Table 2: Softwire46 Sub-attributes

   The following list defines the meaning of the Table 2 entries.

   0     Not permitted
   0-1   Optional; zero or one instance of the attribute may be present.
   1     Mandatory; only one instance of the attribute must be present.
   1+    Mandatory; one or more instances of the attribute may be
         present.

3.1.3.  Specification of the Softwire46 Sub-attributes

3.1.3.1.  Softwire46-Rule Attribute

   Softwire46-Rule can only be encapsulated in Softwire46-MAP-E
   (Section 3.1.1.1) or Softwire46-MAP-T (Section 3.1.1.2).  Depending
   on the deployment scenario, one Basic Mapping Rule (BMR) and zero or
   more Forwarding Mapping Rules (FMRs) MUST be included in
   Softwire46-MAP-E and Softwire46-MAP-T.

   Each type of Softwire46-Rule also contains a number of sub-
   attributes, including Rule-IPv6-Prefix, Rule-IPv4-Prefix, and EA-
   Length.  The structure of the sub-attributes for Softwire46-Rule is
   defined in Section 3.1.4.

   Defining multiple TLV types achieves the same design goals as the
   "Softwire46 Rule Flags" defined in Section 4.1 of [RFC7598].  Using a
   TLV type set to 5 is equivalent to setting the F flag in the
   OPTION_S46_RULE S46 Rule Flags field.

   TLV-Type
      4 Basic Mapping Rule only (not to be used for forwarding)

      5 Forwarding Permitted Mapping Rule

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   Data Type
      The attribute Softwire46-Rule is of type "tlv" (Section 3.13 of
      [RFC8044]).

   TLV-Value
      This field contains a set of attributes as follows:

      Rule-IPv6-Prefix
         This attribute contains the IPv6 prefix for use in the MAP
         rule.  Refer to Section 3.1.4.1.

      Rule-IPv4-Prefix
         This attribute contains the IPv4 prefix for use in the MAP
         rule.  Refer to Section 3.1.4.2.

      EA-Length
         This attribute contains the Embedded Address (EA) bit length.
         Refer to Section 3.1.4.3.

3.1.3.2.  Softwire46-BR Attribute

   Softwire46-BR can only be encapsulated in Softwire46-MAP-E
   (Section 3.1.1.1) or Softwire46-Lightweight-4over6 (Section 3.1.1.3).

   There MUST be at least one Softwire46-BR included in each
   Softwire46-MAP-E or Softwire46-Lightweight-4over6.

   The structure of Softwire46-BR is shown below:

   TLV-Type
      6

   TLV-Length
      18 octets

   Data Type
      The attribute Softwire46-BR is of type "ipv6addr" (Section 3.9 of
      [RFC8044]).

   TLV-Value
      br-ipv6-address.  A fixed-length field of 16 octets that specifies
      the IPv6 address for the Softwire46 Border Relay (BR).

3.1.3.3.  Softwire46-DMR Attribute

   Softwire46-DMR may only appear in Softwire46-MAP-T (Section 3.1.1.2).
   There MUST be exactly one Softwire46-DMR included in one Softwire46-
   MAP-T.

   The structure of Softwire46-DMR is shown below:

   TLV-Type
      7

   TLV-Length
      4 + length of dmr-ipv6-prefix specified in octets.

   Data Type
      The attribute Softwire46-DMR is of type "ipv6prefix" (Section 3.10
      of [RFC8044]).

   TLV-Value
      A variable-length (dmr-prefix6-len) field specifying the IPv6
      prefix (dmr-ipv6-prefix) for the BR.  This field is right-padded
      with zeros to the nearest octet boundary when dmr-prefix6-len is
      not divisible by 8.  Prefixes with lengths from 0 to 96 are
      allowed.

3.1.3.4.  Softwire46-V4V6Bind Attribute

   Softwire46-V4V6Bind may only be encapsulated in Softwire46-
   Lightweight-4over6 (Section 3.1.1.3).  There MUST be exactly one
   Softwire46-V4V6Bind included in each Softwire46-Lightweight-4over6.

   The structure of Softwire46-V4V6Bind is shown below:

   TLV-Type
      8

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   Data Type
      The attribute Softwire46-V4V6Bind is of type "tlv" (Section 3.13
      of [RFC8044]).

   TLV-Value
      This field contains a set of attributes as follows:

      IPv4-Address
         This attribute contains an IPv4 address, used to specify the
         full or shared IPv4 address of the CE.  Refer to
         Section 3.1.5.1.

      Bind-IPv6-Prefix
         This attribute contains an IPv6 prefix used to indicate which
         configured prefix the Softwire46 CE should use for constructing
         the softwire.  Refer to Section 3.1.5.2.

3.1.3.5.  Softwire46-PORTPARAMS Attribute

   Softwire46-PORTPARAMS is optional.  It is used to specify port set
   information for IPv4 address sharing between clients.
   Softwire46-PORTPARAMS MAY be included in any of the Softwire46
   attributes.

   The structure of Softwire46-PORTPARAMS is shown below:

   TLV-Type
      9

   TLV-Length
      Indicates the length of this attribute, including the TLV-Type,
      TLV-Length, and TLV-Value fields.

   Data Type
      The attribute Softwire46-PORTPARAMS is of type "tlv" (Section 3.13
      of [RFC8044]).

   TLV-Value
      This field contains a set of attributes as follows:

      PSID-Offset
         This attribute specifies the numeric value for the Softwire46
         algorithm's excluded port range/offset bits (a bits).  Refer to
         Section 3.1.6.1.

      PSID-Len
         This attribute specifies the number of significant bits in the
         PSID field (also known as 'k').  Refer to Section 3.1.6.2.

      PSID
         This attribute specifies the PSID value.  Refer to
         Section 3.1.6.3.

3.1.4.  Sub-attributes for Softwire46-Rule

   There are two types of Softwire46-Rule: the Basic Mapping Rule and
   the Forwarding Mapping Rule, indicated by the value in the TLV-Type
   field of Softwire46-Rule (Section 3.1.3.1).

   Each type of Softwire46-Rule also contains a number of sub-attributes
   as detailed in the following subsections.

3.1.4.1.  Rule-IPv6-Prefix Attribute

   Rule-IPv6-Prefix is REQUIRED for every Softwire46-Rule.  There MUST
   be exactly one Rule-IPv6-Prefix encapsulated in each type of
   Softwire46-Rule.

   Rule-IPv6-Prefix follows the framed IPv6 prefix designed in [RFC3162]
   and [RFC8044].

   The structure of Rule-IPv6-Prefix is shown below:

   TLV-Type
      10

   TLV-Length
      4 + length of rule-ipv6-prefix specified in octets.

   Data Type
      The attribute Rule-IPv6-Prefix is of type "ipv6prefix"
      (Section 3.10 of [RFC8044]).

   TLV-Value
      A variable-length field that specifies an IPv6 prefix (rule-
      ipv6-prefix) appearing in the MAP rule.

3.1.4.2.  Rule-IPv4-Prefix Attribute

   This attribute is used to convey the MAP Rule IPv4 prefix.  The
   structure of Rule-IPv4-Prefix is shown below:

   TLV-Type
      11

   TLV-Length
      4 + length of rule-ipv4-prefix specified in octets.

   Data Type
      The attribute Rule-IPv4-Prefix is of type "ipv4prefix"
      (Section 3.11 of [RFC8044]).

   TLV-Value
      A variable-length field that specifies an IPv4 prefix (rule-
      ipv4-prefix) appearing in the MAP rule.

3.1.4.3.  EA-Length Attribute

   This attribute is used to convey the Embedded Address (EA) bit
   length.  The structure of EA-Length is shown below:

   TLV-Type
      12

   TLV-Length
      6 octets

   Data Type
      The attribute EA-Length is of type "integer" (Section 3.1 of
      [RFC8044]).

   TLV-Value
      EA-len; 32 bits long.  Specifies the Embedded Address (EA) bit
      length.  Allowed values range from 0 to 48.

3.1.5.  Attributes for Softwire46-v4v6Bind

3.1.5.1.  IPv4-Address Attribute

   The IPv4-Address MAY be used to specify the full or shared IPv4
   address of the CE.

   The structure of IPv4-Address is shown below:

   TLV-Type
      13

   TLV-Length
      6 octets

   Data Type
      The attribute IPv4-Address is of type "ipv4addr" (Section 3.8 of
      [RFC8044]).

   TLV-Value
      32 bits long.  Specifies the IPv4 address (ipv4-address) to appear
      in Softwire46-V4V6Bind (Section 3.1.3.4).

3.1.5.2.  Bind-IPv6-Prefix Attribute

   The Bind-IPv6-Prefix is used by the CE to identify the correct IPv6
   prefix to be used as the tunnel source.

   The structure of Bind-IPv6-Prefix is shown below:

   TLV-Type
      14

   TLV-Length
      4 + length of bind-ipv6-prefix specified in octets.

   Data Type
      The attribute Bind-IPv6-Prefix is of type "ipv6prefix"
      (Section 3.10 of [RFC8044]).

   TLV-Value
      A variable-length field specifying the IPv6 prefix or address for
      the Softwire46 CE (bind-ipv6-prefix).  This field is right-padded
      with zeros to the nearest octet boundary when the prefix length is
      not divisible by 8.

3.1.6.  Attributes for Softwire46-PORTPARAMS

3.1.6.1.  PSID-Offset Attribute

   This attribute is used to convey the Port Set Identifier offset as
   defined in [RFC7597].  This attribute is encoded in 32 bits as per
   the recommendation in Appendix A.2.1 of [RFC6158].

   The structure of PSID-Offset is shown below:

   TLV-Type
      15

   TLV-Length
      6 octets

   Data Type
      The attribute PSID-Offset is of type "integer" (Section 3.1 of
      [RFC8044]).

   TLV-Value
      Contains the PSID-Offset (8 bits) right justified, and the unused
      bits in this field MUST be set to zero.  This field specifies the
      numeric value for the Softwire46 algorithm's excluded port range/
      offset bits (a bits), as per Section 5.1 of [RFC7597].

      Default values for this field are specific to the softwire
      mechanism being implemented and are defined in the relevant
      specification document.

3.1.6.2.  PSID-Len Attribute

   This attribute is used to convey the PSID length as defined in
   [RFC7597].  This attribute is encoded in 32 bits as per the
   recommendation in Appendix A.2.1 of [RFC6158].

   The structure of PSID-Len is shown below:

   TLV-Type
      16

   TLV-Length
      6 octets

   Data Type
      The attribute PSID-Len is of type "integer" (Section 3.1 of
      [RFC8044]).

   TLV-Value
      Contains the PSID-len (8 bits) right justified, and the unused
      bits in this field MUST be set to zero.  This field specifies the
      number of significant bits in the PSID field (also known as 'k').
      When set to 0, the PSID field is to be ignored.  After the first a
      bits, there are k bits in the port number representing the value
      of the PSID.  Subsequently, the address-sharing ratio would be
      2^k.

3.1.6.3.  PSID Attribute

   This attribute is used to convey the PSID as defined in [RFC7597].
   This attribute is encoded in 32 bits as per the recommendation in
   Appendix A.2.1 of [RFC6158].

   The structure of PSID is shown below:

   TLV-Type
      17

   TLV-Length
      6 octets

   Data Type
      The attribute PSID is of type "integer" (Section 3.1 of
      [RFC8044]).

   TLV-Value
      Contains the PSID (16 bits) right justified, and the unused bits
      in this field MUST be set to zero.

      The PSID value algorithmically identifies a set of ports assigned
      to a CE.  The first k bits on the left of this 2-octet field are
      the PSID value.  The remaining (16-k) bits on the right are
      padding zeros.

3.2.  Softwire46-Priority Attribute

   The Softwire46-Priority Attribute includes an ordered list of
   Softwire46 mechanisms allowing the client to prioritize which
   mechanism to use, corresponding to OPTION_S46_PRIORITY defined in
   [RFC8026].  The following requirements apply:

      The Softwire46-Priority Attribute MAY appear in an Access-Accept
      packet.  It MAY also appear in an Access-Request packet.

      The Softwire46-Priority Attribute MAY appear in a CoA-Request
      packet.

      The Softwire46-Priority Attribute MAY appear in an Accounting-
      Request packet.

      The Softwire46-Priority Attribute MUST NOT appear in any other
      RADIUS packet.

   The Softwire46-Priority Attribute is structured as follows:

   Type
      241

   Length
      Indicates the length of this attribute, including the Type,
      Length, Extended-Type and Value fields.

   Extended-Type
      10

   TLV-Value
      The attribute includes one or more Softwire46-Option-Code TLVs: A
      Softwire46-Priority Attribute MUST contain at least one
      Softwire46-Option-Code TLV (Section 3.2.1).

      Softwire46 mechanisms are prioritized in the appearance order in
      the Softwire46-Priority Attribute.  That is, the first-appearing
      mechanism is most preferred.

   The Softwire46-Priority Attribute is associated with the following
   identifier: 241.10.

3.2.1.  Softwire46-Option-Code

   This attribute is used to convey an option code assigned to a
   Softwire46 mechanism [RFC8026].  This attribute is encoded in 32 bits
   as per the recommendation in Appendix A.2.1 of [RFC6158].

   The structure of Softwire46-Option-Code is shown below:

   TLV-Type
      18

   TLV-Length
      6 octets

   Data Type
      The attribute Softwire46-Option-Code is of type "integer"
      (Section 3.1 of [RFC8044]).

   TLV-Value
      A 32-bit IANA-registered option code representing a Softwire46
      mechanism (Softwire46-option-code).  The codes and their
      corresponding Softwire46 mechanisms are listed in Section 7.3.

3.3.  Softwire46-Multicast Attribute

   The Softwire46-Multicast Attribute conveys the IPv6 prefixes to be
   used to synthesize multicast and unicast IPv4-embedded IPv6 addresses
   as per [RFC8114].  This attribute is of type "tlv" and contains
   additional TLVs.  The following requirements apply:

   *  The BNG SHALL use the IPv6 prefixes returned in the RADIUS
      Softwire46-Multicast Attribute to populate the DHCPv6 PREFIX64
      Option [RFC8115].

   *  This attribute MAY be used in Access-Request packets as a hint to
      the RADIUS server.  For example, if the BNG is preconfigured for
      Softwire46-Multicast, these prefixes may be inserted in the
      attribute.  The RADIUS server MAY ignore the hint sent by the BNG,
      and it MAY assign a different Softwire46-Multicast Attribute.

   *  The Softwire46-Multicast Attribute MAY appear in an Access-
      Request, Access-Accept, CoA-Request, and Accounting-Request
      packet.

   *  The Softwire46-Multicast Attribute MUST NOT appear in any other
      RADIUS packet.

   *  The Softwire46-Multicast Attribute MAY contain ASM-Prefix64
      (Section 3.3.1), SSM-Prefix64 (Section 3.3.2), and U-Prefix64
      (Section 3.3.3).

   *  The Softwire46-Multicast Attribute MUST include ASM-Prefix64 or
      SSM-Prefix64, and it MAY include both.

   *  The U-Prefix64 MUST be present when SSM-Prefix64 is present.
      U-Prefix64 MAY be present when ASM-Prefix64 is present.

   The Softwire46-Multicast Attribute is structured as follows:

   Type
      241

   Length
      This field indicates the total length in bytes of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded attributes.

   Extended-Type
      11

   Value
      This field contains a set of attributes as follows:

      ASM-Prefix64
         This attribute contains the Any-Source Multicast (ASM) IPv6
         prefix.  Refer to Section 3.3.1.

      SSM-Prefix64
         This attribute contains the Source-Source Multicast (SSM) IPv6
         prefix.  Refer to Section 3.3.2.

      U-Prefix64
         This attribute contains the IPv4 prefix used for address
         translation.  Refer to Section 3.3.3.

   The Softwire46-Multicast Attribute is associated with the following
   identifier: 241.11.

3.3.1.  ASM-Prefix64 Attribute

   The ASM-Prefix64 attribute is structured as follows:

   TLV-Type
      19

   TLV-Length
      16 octets.  The length of asm-prefix64 must be /96 [RFC8115].

   Data Type
      The attribute ASM-Prefix64 is of type "ipv6prefix" (Section 3.10
      of [RFC8044]).

   TLV-Value
      This field specifies the IPv6 multicast prefix (asm-prefix64) to
      be used to synthesize the IPv4-embedded IPv6 addresses of the
      multicast groups in the ASM mode.  The conveyed multicast IPv6
      prefix MUST belong to the ASM range.

3.3.2.  SSM-Prefix64 Attribute

   The SSM-Prefix64 attribute is structured as follows:

   Type
      20

   TLV-Length
      16 octets.  The length of ssm-prefix64 must be /96 [RFC8115].

   Data Type
      The attribute SSM-Prefix64 is of type "ipv6prefix" (Section 3.10
      of [RFC8044]).

   TLV-Type
      This field specifies the IPv6 multicast prefix (ssm-prefix64) to
      be used to synthesize the IPv4-embedded IPv6 addresses of the
      multicast groups in the SSM mode.  The conveyed multicast IPv6
      prefix MUST belong to the SSM range.

3.3.3.  U-Prefix64 Attribute

   The structure of U-Prefix64 is shown below:

   TLV-Type
      21

   TLV-Length
      4 + length of unicast-prefix.  As specified in [RFC6052], the
      unicast-prefix prefix length MUST be set to 32, 40, 48, 56, 64, or
      96.

   Data Type
      The attribute U-Prefix64 is of type "ipv6prefix" (Section 3.10 of
      [RFC8044]).

   TLV-Value
      This field identifies the IPv6 unicast prefix (u-prefix64) to be
      used in the SSM mode for constructing the IPv4-embedded IPv6
      addresses representing the IPv4 multicast sources in the IPv6
      domain.  It may also be used to extract the IPv4 address from the
      received multicast data flows.

4.  A Sample Configuration Process with RADIUS

   Figure 2 illustrates how the RADIUS and DHCPv6 protocols interwork to
   provide CE with softwire configuration information.


   CE                             BNG                     AAA Server
   |                               |                               |
   |-------1.DHCPv6 Solicit------->|                               |
   |(ORO with unicast and/or       |                               |
   |    multicast container option |                               |
   |    codes(s))                  |                               |
   |                               |-------2.Access-Request------->|
   |                               |   (Softwire46-Configuration   |
   |                               |       Attribute and/or        |
   |                               |Softwire46-Multicast Attribute)|
   |                               |                               |
   |                               |<------3.Access-Accept---------|
   |                               |   (Softwire46-Configuration   |
   |                               |       Attribute and/or        |
   |                               |Softwire46-Multicast Attribute)|
   |                               |                               |
   |<----4.DHCPv6 Advertisement----|                               |
   |     (container option(s))     |                               |
   |                               |                               |
   |-------5.DHCPv6  Request------>|                               |
   |     (container option(s))     |                               |
   |                               |                               |
   |<--------6.DHCPv6 Reply--------|                               |
   |     (container option(s))     |                               |
   |                               |                               |
                DHCPv6                         RADIUS

          Figure 2: Interaction between DHCPv6 and AAA Server with
                           RADIUS Authentication

   1.  The CE creates a DHCPv6 Solicit message.  For unicast softwire
       configuration, the message includes an OPTION_REQUEST_OPTION (6)
       with the Softwire46 Container option code(s) as defined in
       [RFC7598].  OPTION_S46_CONT_MAPE (94) should be included for MAP-
       E, OPTION_S46_CONT_MAPT (95) for MAP-T, and OPTION_S46_CONT_LW
       (96) for Lightweight 4over6.  For multicast configuration, the
       option number for OPTION_V6_PREFIX64 (113) is included in the
       client's Option Request Option (ORO).  The message is sent to the
       BNG.

   2.  On receipt of the DHCPv6 Solicit message, the BNG constructs a
       RADIUS Access-Request message containing a User-Name Attribute
       (1) (containing either a CE Media Access Control (MAC) address,
       interface-id, or both) and a User-Password Attribute (2) (with a
       preconfigured shared password between the CE and AAA server as
       defined in [RFC2865]).  The Softwire46-Configuration Attribute
       and/or Softwire46-Multicast Attribute are also included (as
       requested by the client).  The resulting message is sent to the
       AAA server.

   3.  The AAA server authenticates the request.  If this is successful,
       and a suitable configuration is available, an Access-Accept
       message is sent to the BNG containing the requested
       Softwire46-Configuration Attribute or Softwire46-Multicast
       Attribute.  It is the responsibility of the AAA server to ensure
       the consistency of the provided configuration.

   4.  The BNG maps the received softwire configuration into the
       corresponding fields in the DHCPv6 softwire configuration
       option(s).  These are included in the DHCPv6 Advertise message,
       which is sent to the CE.

   5.  The CE sends a DHCPv6 Request message.  In the ORO, the option
       codes of any of the required softwire options that were received
       in the DHCPv6 Advertise message are included.

   6.  The BNG sends a DHCPv6 Reply message to the client containing the
       softwire container option(s) enumerated in the ORO.

   The authorization operation could be done independently after the
   authentication process.  In this case, steps 1-5 are completed as
   above, then the following steps are performed:

   6a.  When the BNG receives the DHCPv6 Request, it constructs a RADIUS
        Access-Request message, which contains a Service-Type Attribute
        (6) with the value "Authorize Only" (17), the corresponding
        Softwire46-Configuration Attribute, and a State Attribute
        obtained from the previous authentication process according to
        [RFC5080].  The resulting message is sent to the AAA server.

   7a.  The AAA server checks the authorization request.  If it is
        approved, an Access-Accept message is returned to the BNG with
        the corresponding Softwire46-Configuration Attribute.

   8a.  The BNG sends a Reply message to the client containing the
        softwire container options enumerated in the ORO.

   In addition to the above, the following points need to be considered:

   *  In the configuration message flows described above, the Message-
      Authenticator (type 80) [RFC2869] should be used to protect both
      Access-Request and Access-Accept messages.

   *  If the BNG does not receive the corresponding
      Softwire46-Configuration Attribute in the Access-Accept message,
      it may fall back to creating the DHCPv6 softwire configuration
      options using the preconfigured Softwire46 configuration if this
      is present.

   *  If the BNG receives an Access-Reject from the AAA server, then the
      Softwire46 configuration must not be supplied to the client.

   *  As specified in Section 18.2.5 of [RFC8415] ("Creation and
      Transmission of Rebind Messages") if the DHCPv6 server to which
      the DHCPv6 Renew message was sent at time T1 has not responded by
      time T2, the CE (DHCPv6 client) should enter the Rebind state and
      attempt to contact any available server.  In this situation, a
      secondary BNG receiving the DHCPv6 message must initiate a new
      Access-Request message towards the AAA server.  The secondary BNG
      includes the Softwire46-Configuration Attribute in this Access-
      Request message.

   *  For Lightweight 4over6, the CE's binding state needs to be
      synchronized between the clients and the Lightweight AFTR
      (lwAFTR)/BR.  This can be achieved in two ways: static
      preconfiguration of the bindings on both the AAA server and lwAFTR
      or on demand, whereby the AAA server updates the lwAFTR with the
      CE's binding state as it is created or deleted.

   In some deployments, the DHCP server may use the Accounting-Request
   to report the softwire configuration returned to a requesting host to
   a AAA server.  It is the responsibility of the DHCP server to ensure
   the consistency of the configuration provided to the requesting
   hosts.  Reported data to a AAA server may be required for various
   operational purposes (e.g., regulatory).

   A configuration change (e.g., BR address) may result in an exchange
   of CoA-Requests between the BNG and the AAA server, as shown in
   Figure 3.  Concretely, when the BNG receives a CoA-Request message
   containing Softwire46 attributes, it sends a DHCPv6 Reconfigure
   message to the appropriate CE to inform that CE that an updated
   configuration is available.  Upon receipt of such a message, the CE
   sends a DHCPv6 Renew or Information-Request in order to receive the
   updated Softwire46 configuration.  In deployments where the BNG
   embeds a DHCPv6 relay, CoA-Requests can be used following the
   procedure specified in [RFC6977].

           CE                          BNG                    AAA Server
           |                           |                            |
           |---DHCPv6 Solicit--------->|                            |
           |                           |---Access-Request---------->|
           |                           |<--Access-Accept------------|
           |                           |(Softwire46-Configuration   |
           |                           |    Attribute ...)          |
                                     ....
           |                           |                            |
           |                           |<-----CoA-Request-----------|
           |                           |(Softwire46-Configuration   |
           |                           |    Attribute ...)          |
           |                           |------CoA-Response--------->|
           |<--DHCPv6 Reconfigure------|                            |
           |                           |                            |
                                     ....

                 Figure 3: Change of Configuration Example

5.  Table of Attributes

   This document specifies three new RADIUS attributes, and their
   formats are as follows:

   *  Softwire46-Configuration Attribute: 241.9

   *  Softwire46-Priority Attribute: 241.10

   *  Softwire46-Multicast Attribute: 241.11

   Table 3 describes which attributes may be found in which kinds of
   packets and in what quantity.

   +-------+------+------+---------+----+-------+------+---------------+
   |Request|Accept|Reject|Challenge|Acct|CoA-Req| #    | Attribute     |
   |       |      |      |         |Req |       |      |               |
   +=======+======+======+=========+====+=======+======+===============+
   | 0-1   | 0-1  | 0    | 0       |0-1 | 0-1   |241.9 | Softwire46-   |
   |       |      |      |         |    |       |      | Configuration |
   +-------+------+------+---------+----+-------+------+---------------+
   | 0-1   | 0-1  | 0    | 0       |0-1 | 0-1   |241.10| Softwire46-   |
   |       |      |      |         |    |       |      | Priority      |
   +-------+------+------+---------+----+-------+------+---------------+
   | 0-1   | 0-1  | 0    | 0       |0-1 | 0-1   |241.11| Softwire46-   |
   |       |      |      |         |    |       |      | Multicast     |
   +-------+------+------+---------+----+-------+------+---------------+

                        Table 3: Table of Attributes

6.  Security Considerations

   Section 9 of [RFC7596] discusses security issues related to
   Lightweight 4over6; Section 10 of [RFC7597] discusses security issues
   related to MAP-E; Section 13 of [RFC7599] discusses security issues
   related to MAP-T; and Section 9 of [RFC8114] discusses security
   issues related to the delivery of IPv4 multicast services to IPv4
   clients over an IPv6 multicast network.

   This document does not introduce any security issues inherently
   different from those already identified in Section 8 of [RFC2865] and
   Section 6 of [RFC5176] for CoA messages.  Known security
   vulnerabilities of the RADIUS protocol discussed in Section 7 of
   [RFC2607] and Section 7 of [RFC2869] apply to this specification.
   These well-established properties of the RADIUS protocol place some
   limitations on how it can safely be used, since there is some
   inherent requirement to trust the counterparty to not misbehave.

   Accordingly, this document targets deployments where a trusted
   relationship is in place between the RADIUS client and server, with
   communication optionally secured by IPsec or Transport Layer Security
   (TLS) [RFC6614].  The use of IPsec [RFC4301] for providing security
   when RADIUS is carried in IPv6 is discussed in [RFC3162].

   Security considerations for interactions between a Softwire46 CE and
   the BNG are discussed in Section 9 of [RFC7598] (DHCPv6 options for
   the configuration of Softwire46 address and port-mapped clients),
   Section 3 of [RFC8026] (a DHCPv6-based Softwire46 prioritization
   mechanism), and Section 5 of [RFC8115] (DHCPv6 options for
   configuration of IPv4-embedded IPv6 prefixes).

7.  IANA Considerations

   IANA has made new code point assignments for RADIUS attributes as
   described in the following subsections.  The assignments should use
   the RADIUS registry available at <https://www.iana.org/assignments/
   radius-types/>.

7.1.  New RADIUS Attributes

   IANA has assigned the attribute types defined in this document from
   the RADIUS namespace as described in Section 2 (IANA Considerations)
   of [RFC3575], in accordance with BCP 26 [RFC8126].

   IANA has registered three new RADIUS attributes from the "Short
   Extended Space" section of [RFC6929].  The attributes are the
   Softwire46-Configuration Attribute, Softwire46-Priority Attribute,
   and Softwire46-Multicast Attribute:

      +--------+--------------------------+-----------+-------------+
      | Type   | Description              | Data Type | Reference   |
      +========+==========================+===========+=============+
      | 241.9  | Softwire46-Configuration | tlv       | Section 3.1 |
      +--------+--------------------------+-----------+-------------+
      | 241.10 | Softwire46-Priority      | tlv       | Section 3.2 |
      +--------+--------------------------+-----------+-------------+
      | 241.11 | Softwire46-Multicast     | tlv       | Section 3.3 |
      +--------+--------------------------+-----------+-------------+

                       Table 4: New RADIUS Attributes

7.2.  RADIUS Softwire46 Configuration and Multicast Attributes

   IANA has created a new registry called "RADIUS Softwire46
   Configuration and Multicast Attributes".

   All attributes in this registry have one or more parent RADIUS
   attributes in nesting (refer to [RFC6929]).

   This registry has been initially populated with the following values:

    +--------+-------------------------------+------------+-----------+
    | Value  | Description                   | Data Type  | Reference |
    +========+===============================+============+===========+
    | 0      | Reserved                      |            |           |
    +--------+-------------------------------+------------+-----------+
    | 1      | Softwire46-MAP-E              | tlv        | Section   |
    |        |                               |            | 3.1.1.1   |
    +--------+-------------------------------+------------+-----------+
    | 2      | Softwire46-MAP-T              | tlv        | Section   |
    |        |                               |            | 3.1.1.2   |
    +--------+-------------------------------+------------+-----------+
    | 3      | Softwire46-Lightweight-4over6 | tlv        | Section   |
    |        |                               |            | 3.1.1.3   |
    +--------+-------------------------------+------------+-----------+
    | 4      | Softwire46-Rule (BMR)         | tlv        | Section   |
    |        |                               |            | 3.1.3.1   |
    +--------+-------------------------------+------------+-----------+
    | 5      | Softwire46-Rule (FMR)         | tlv        | Section   |
    |        |                               |            | 3.1.3.1   |
    +--------+-------------------------------+------------+-----------+
    | 6      | Softwire46-BR                 | ipv6addr   | Section   |
    |        |                               |            | 3.1.3.2   |
    +--------+-------------------------------+------------+-----------+
    | 7      | Softwire46-DMR                | ipv6prefix | Section   |
    |        |                               |            | 3.1.3.3   |
    +--------+-------------------------------+------------+-----------+
    | 8      | Softwire46-V4V6Bind           | tlv        | Section   |
    |        |                               |            | 3.1.3.4   |
    +--------+-------------------------------+------------+-----------+
    | 9      | Softwire46-PORTPARAMS         | tlv        | Section   |
    |        |                               |            | 3.1.3.5   |
    +--------+-------------------------------+------------+-----------+
    | 10     | Rule-IPv6-Prefix              | ipv6prefix | Section   |
    |        |                               |            | 3.1.4.1   |
    +--------+-------------------------------+------------+-----------+
    | 11     | Rule-IPv4-Prefix              | ipv4prefix | Section   |
    |        |                               |            | 3.1.4.2   |
    +--------+-------------------------------+------------+-----------+
    | 12     | EA-Length                     | integer    | Section   |
    |        |                               |            | 3.1.4.3   |
    +--------+-------------------------------+------------+-----------+
    | 13     | IPv4-Address                  | ipv4addr   | Section   |
    |        |                               |            | 3.1.5.1   |
    +--------+-------------------------------+------------+-----------+
    | 14     | Bind-IPv6-Prefix              | ipv6prefix | Section   |
    |        |                               |            | 3.1.5.2   |
    +--------+-------------------------------+------------+-----------+
    | 15     | PSID-Offset                   | integer    | Section   |
    |        |                               |            | 3.1.6.1   |
    +--------+-------------------------------+------------+-----------+
    | 16     | PSID-Len                      | integer    | Section   |
    |        |                               |            | 3.1.6.2   |
    +--------+-------------------------------+------------+-----------+
    | 17     | PSID                          | integer    | Section   |
    |        |                               |            | 3.1.6.3   |
    +--------+-------------------------------+------------+-----------+
    | 18     | Softwire46-Option-Code        | integer    | Section   |
    |        |                               |            | 3.2.1     |
    +--------+-------------------------------+------------+-----------+
    | 19     | ASM-Prefix64                  | ipv6prefix | Section   |
    |        |                               |            | 3.3.1     |
    +--------+-------------------------------+------------+-----------+
    | 20     | SSM-Prefix64                  | ipv6prefix | Section   |
    |        |                               |            | 3.3.2     |
    +--------+-------------------------------+------------+-----------+
    | 21     | U-Prefix64                    | ipv6prefix | Section   |
    |        |                               |            | 3.3.3     |
    +--------+-------------------------------+------------+-----------+
    | 22-255 | Unassigned                    |            |           |
    +--------+-------------------------------+------------+-----------+

     Table 5: RADIUS Softwire46 Configuration and Multicast Attributes

   The registration procedure for this registry is Standards Action as
   defined in [RFC8126].

7.3.  Softwire46 Mechanisms and Their Identifying Option Codes

   The Softwire46-Priority Attribute conveys an ordered list of option
   codes assigned to Softwire46 mechanisms, for which IANA has created
   and will maintain a new registry titled "Option Codes Permitted in
   the Softwire46-Priority Attribute".

   Table 6 shows the initial version of allowed option codes and the
   Softwire46 mechanisms that they represent.  The option code for DS-
   Lite is derived from the IANA-allocated RADIUS Attribute Type value
   for DS-Lite [RFC6519].  The option codes for MAP-E, MAP-T, and
   Lightweight 4over6 are the TLV-Type values for the MAP-E, MAP-T, and
   Lightweight 4over6 attributes defined in Section 3.1.1.

            +-------------+----------------------+-----------+
            | Option Code | Softwire46 Mechanism | Reference |
            +=============+======================+===========+
            | 1           | MAP-E                | [RFC7597] |
            +-------------+----------------------+-----------+
            | 2           | MAP-T                | [RFC7599] |
            +-------------+----------------------+-----------+
            | 3           | Lightweight 4over6   | [RFC7596] |
            +-------------+----------------------+-----------+
            | 144         | DS-Lite              | [RFC6519] |
            +-------------+----------------------+-----------+

                 Table 6: Option Codes to S46 Mechanisms

   Additional option codes may be added to this list in the future using
   the IETF Review process described in Section 4.8 of [RFC8126].

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <https://www.rfc-editor.org/info/rfc2865>.

   [RFC3162]  Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
              RFC 3162, DOI 10.17487/RFC3162, August 2001,
              <https://www.rfc-editor.org/info/rfc3162>.

   [RFC3575]  Aboba, B., "IANA Considerations for RADIUS (Remote
              Authentication Dial In User Service)", RFC 3575,
              DOI 10.17487/RFC3575, July 2003,
              <https://www.rfc-editor.org/info/rfc3575>.

   [RFC5080]  Nelson, D. and A. DeKok, "Common Remote Authentication
              Dial In User Service (RADIUS) Implementation Issues and
              Suggested Fixes", RFC 5080, DOI 10.17487/RFC5080, December
              2007, <https://www.rfc-editor.org/info/rfc5080>.

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              DOI 10.17487/RFC5176, January 2008,
              <https://www.rfc-editor.org/info/rfc5176>.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              DOI 10.17487/RFC6052, October 2010,
              <https://www.rfc-editor.org/info/rfc6052>.

   [RFC6158]  DeKok, A., Ed. and G. Weber, "RADIUS Design Guidelines",
              BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011,
              <https://www.rfc-editor.org/info/rfc6158>.

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929,
              DOI 10.17487/RFC6929, April 2013,
              <https://www.rfc-editor.org/info/rfc6929>.

   [RFC8026]  Boucadair, M. and I. Farrer, "Unified IPv4-in-IPv6
              Softwire Customer Premises Equipment (CPE): A DHCPv6-Based
              Prioritization Mechanism", RFC 8026, DOI 10.17487/RFC8026,
              November 2016, <https://www.rfc-editor.org/info/rfc8026>.

   [RFC8044]  DeKok, A., "Data Types in RADIUS", RFC 8044,
              DOI 10.17487/RFC8044, January 2017,
              <https://www.rfc-editor.org/info/rfc8044>.

   [RFC8115]  Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6
              Option for IPv4-Embedded Multicast and Unicast IPv6
              Prefixes", RFC 8115, DOI 10.17487/RFC8115, March 2017,
              <https://www.rfc-editor.org/info/rfc8115>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

8.2.  Informative References

   [LIGHTWEIGHT-4OVER6]
              Xie, C., Sun, Q., Qiong, Q., Zhou, C., Tsou, T., and Z.
              Liu, "Radius Extension for Lightweight 4over6", Work in
              Progress, Internet-Draft, draft-sun-softwire-lw4over6-
              radext-01, 6 March 2014, <https://tools.ietf.org/html/
              draft-sun-softwire-lw4over6-radext-01>.

   [RADIUS-EXT]
              Wang, Q., Meng, W., Wang, C., and M. Boucadair, "RADIUS
              Extensions for IPv4-Embedded Multicast and Unicast IPv6
              Prefixes", Work in Progress, Internet-Draft, draft-wang-
              radext-multicast-radius-ext-00, 2 December 2015,
              <https://tools.ietf.org/html/draft-wang-radext-multicast-
              radius-ext-00>.

   [RFC2607]  Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
              Implementation in Roaming", RFC 2607,
              DOI 10.17487/RFC2607, June 1999,
              <https://www.rfc-editor.org/info/rfc2607>.

   [RFC2869]  Rigney, C., Willats, W., and P. Calhoun, "RADIUS
              Extensions", RFC 2869, DOI 10.17487/RFC2869, June 2000,
              <https://www.rfc-editor.org/info/rfc2869>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [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>.

   [RFC6519]  Maglione, R. and A. Durand, "RADIUS Extensions for Dual-
              Stack Lite", RFC 6519, DOI 10.17487/RFC6519, February
              2012, <https://www.rfc-editor.org/info/rfc6519>.

   [RFC6614]  Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
              "Transport Layer Security (TLS) Encryption for RADIUS",
              RFC 6614, DOI 10.17487/RFC6614, May 2012,
              <https://www.rfc-editor.org/info/rfc6614>.

   [RFC6977]  Boucadair, M. and X. Pougnard, "Triggering DHCPv6
              Reconfiguration from Relay Agents", RFC 6977,
              DOI 10.17487/RFC6977, July 2013,
              <https://www.rfc-editor.org/info/rfc6977>.

   [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>.

   [RFC8114]  Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
              Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
              over an IPv6 Multicast Network", RFC 8114,
              DOI 10.17487/RFC8114, March 2017,
              <https://www.rfc-editor.org/info/rfc8114>.

Appendix A.  DHCPv6 to RADIUS Field Mappings

   The following sections detail the mappings between the softwire
   DHCPv6 option fields and the relevant RADIUS attributes as defined in
   this document.

A.1.  OPTION_S46_RULE (89) to Softwire46-Rule Sub-TLV Field Mappings

    +-----------------------+----------------------+------------------+
    | OPTION_S46_RULE Field | Softwire46-Rule Name |   TLV Subfield   |
    +=======================+======================+==================+
    |         flags         |         N/A          | TLV-type (4, 5)  |
    +-----------------------+----------------------+------------------+
    |         ea-len        |      EA-Length       |      EA-len      |
    +-----------------------+----------------------+------------------+
    |      prefix4-len      |   Rule-IPv4-Prefix   |  Prefix-Length   |
    +-----------------------+----------------------+------------------+
    |      ipv4-prefix      |   Rule-IPv4-Prefix   | rule-ipv4-prefix |
    +-----------------------+----------------------+------------------+
    |      prefix6-len      |   Rule-IPv6-Prefix   |  Prefix-Length   |
    +-----------------------+----------------------+------------------+
    |      ipv6-prefix      |   Rule-IPv6-Prefix   | rule-ipv6-prefix |
    +-----------------------+----------------------+------------------+

     Table 7: OPTION_S46_RULE to Softwire46-Rule Sub-TLV Field Mappings

A.2.  OPTION_S46_BR (90) to Softwire46-BR Field Mappings

             +---------------------+------------------------+
             | OPTION_S46_BR Field | Softwire46-BR Subfield |
             +=====================+========================+
             |   br-ipv6-address   |    br-ipv6-address     |
             +---------------------+------------------------+

                 Table 8: OPTION_S46_BR to Softwire46-BR
                              Field Mappings

A.3.  OPTION_S46_DMR (91) to Softwire46-DMR

            +----------------------+-------------------------+
            | OPTION_S46_DMR Field | Softwire46-DMR Subfield |
            +======================+=========================+
            |   dmr-prefix6-len    |     dmr-prefix6-len     |
            +----------------------+-------------------------+
            |   dmr-ipv6-prefix    |     dmr-ipv6-prefix     |
            +----------------------+-------------------------+

                Table 9: OPTION_S46_DMR to Softwire46-DMR
                              Field Mappings

A.4.  OPTION_S46_V4V6BIND (92) to Softwire46-V4V6Bind

     +---------------------+---------------------+------------------+
     | OPTION_S46_V4V6BIND | Softwire46-V4V6Bind |   TLV Subfield   |
     |        Field        |         Name        |                  |
     +=====================+=====================+==================+
     |     ipv4-address    |     IPv4-Address    |   ipv4-address   |
     +---------------------+---------------------+------------------+
     |   bindprefix6-len   |   Bind-IPv6-Prefix  |  Prefix-Length   |
     +---------------------+---------------------+------------------+
     |   bind-ipv6-prefix  |   Bind-IPv6-Prefix  | bind-ipv6-prefix |
     +---------------------+---------------------+------------------+

           Table 10: OPTION_S46_V4V6BIND to Softwire46-V4V6Bind
                              Field Mappings

A.5.  OPTION_S46_PORTPARAMS (93) to Softwire46-PORTPARAMS Field Mappings

   +-----------------------------+-----------------------+-------------+
   |    OPTION_S46_PORTPARAMS    | Softwire46-PORTPARAMS |     TLV     |
   |            Field            |          Name         |   Subfield  |
   +=============================+=======================+=============+
   |            offset           |      PSID-Offset      | PSID-Offset |
   +-----------------------------+-----------------------+-------------+
   |           PSID-len          |        PSID-Len       |   PSID-len  |
   +-----------------------------+-----------------------+-------------+
   |             PSID            |          PSID         |     PSID    |
   +-----------------------------+-----------------------+-------------+

          Table 11: OPTION_S46_PORTPARAMS to Softwire46-PORTPARAMS
                               Field Mappings

A.6.  OPTION_S46_PRIORITY (111) to Softwire46-PORTPARAMS Field Mappings

          +---------------------------+------------------------+
          | OPTION_S46_PRIORITY Field |  Softwire46-Priority   |
          |                           |   Attribute Subfield   |
          +===========================+========================+
          |      s46-option-code      | Softwire46-option-code |
          +---------------------------+------------------------+

                     Table 12: OPTION_S46_PRIORITY to
                   Softwire46-PORTPARAMS Field Mappings

A.7.  OPTION_V6_PREFIX64 (113) to Softwire46-Multicast Attribute Field
      Mappings

    +--------------------------+----------------------+---------------+
    | OPTION_V6_PREFIX64 Field | Softwire46-Multicast |  TLV Subfield |
    |                          |  Attribute TLV Name  |               |
    +==========================+======================+===============+
    |        asm-length        |     ASM-Prefix64     | Prefix-Length |
    +--------------------------+----------------------+---------------+
    |      ASM_mPrefix64       |     ASM-Prefix64     |  asm-prefix64 |
    +--------------------------+----------------------+---------------+
    |        ssm-length        |     SSM-Prefix64     | Prefix-Length |
    +--------------------------+----------------------+---------------+
    |      SSM_mPrefix64       |     SSM-Prefix64     |  ssm-prefix64 |
    +--------------------------+----------------------+---------------+
    |      unicast-length      |      U-Prefix64      | Prefix-Length |
    +--------------------------+----------------------+---------------+
    |        uPrefix64         |      U-Prefix64      |   u-prefix64  |
    +--------------------------+----------------------+---------------+

    Table 13: OPTION_V6_PREFIX64 to Softwire46-Multicast Field Mappings

Acknowledgements

   The authors would like to thank Peter Lothberg, Wojciech Dec, Ian
   Farrer, Suresh Krishnan, Qian Wang, Wei Meng, Cui Wang, Alan Dekok,
   Stefan Winter, and Yu Tianpeng for their valuable comments regarding
   this document.

   This document was merged with [LIGHTWEIGHT-4OVER6] and [RADIUS-EXT].
   Thanks to everyone who contributed to this document.

   Many thanks to Al Morton, Bernie Volz, Joel Halpern, and Donald
   Eastlake for the review.

Contributors

   Bing Liu
   Huawei Technologies Co., Ltd.
   China

   Email: leo.liubing@huawei.com

   Peter Deacon
   IEA Software, Inc.
   United States of America

   Email: peterd@iea-software.com

   Qiong Sun
   China Telecom
   China

   Email: sunqiong@ctbri.com.cn

   Qi Sun
   Tsinghua University
   China

   Email: sunqibupt@gmail.com

   Cathy Zhou
   Huawei Technologies
   China

   Email: cathy.zhou@huawei.com

   Tina Tsou
   Huawei Technologies (USA)
   United States of America

   Email: Tina.Tsou.Zouting@huawei.com

   ZiLong Liu
   Tsinghua University
   China

   Email: liuzilong8266@126.com

   Yong Cui
   Tsinghua University
   China

   Email: yong@csnet1.cs.tsinghua.edu.cn

Authors' Addresses

   Sheng Jiang (editor)
   China
   Hai-Dian District, Beijing, 100095
   Q14, Huawei Campus, No.156 Beiqing Road
   Huawei Technologies Co., Ltd.

   Email: jiangsheng@huawei.com


   Yu Fu (editor)
   China
   Hai-Dian District, Beijing, 100190
   No.4 South 4th Street, Zhongguancun
   CNNIC

   Email: eleven711711@foxmail.com


   Chongfeng Xie
   China
   Beijing
   China Telecom

   Email: xiechf.bri@chinatelecom.cn


   Tianxiang Li
   China
   100084
   Beijing
   Tsinghua University

   Email: peter416733@gmail.com


   Mohamed Boucadair (editor)
   Orange
   35000 Rennes
   France

   Email: mohamed.boucadair@orange.com


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