RADIUS Attribute for Softwire Address plus Port based Mechanisms
draft-ietf-softwire-map-radius-09

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Document Type Active Internet-Draft (softwire WG)
Last updated 2017-01-03
Replaces draft-jiang-softwire-map-radius
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Softwire                                                   S. Jiang, Ed.
Internet-Draft                              Huawei Technologies Co., Ltd
Intended status: Standards Track                              Y. Fu, Ed.
Expires: July 7, 2017                                              CNNIC
                                                                  B. Liu
                                            Huawei Technologies Co., Ltd
                                                               P. Deacon
                                                      IEA Software, Inc.
                                                                  C. Xie
                                                           China Telecom
                                                                   T. Li
                                                     Tsinghua University
                                                         January 3, 2017

    RADIUS Attribute for Softwire Address plus Port based Mechanisms
                   draft-ietf-softwire-map-radius-09

Abstract

   IPv4-over-IPv6 transition mechanisms provide both IPv4 and IPv6
   connectivity services simultaneously during the IPv4/IPv6 co-existing
   period.  The Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
   options have been defined to configure Customer Edge (CE) in MAP-E,
   MAP-T, and Lightweight 4over6.  However, in many networks, the
   configuration information may be stored in the Authentication
   Authorization and Accounting (AAA) servers, while user configuration
   is mainly provided by the Broadband Network Gateway (BNG) through the
   DHCPv6 protocol.  This document defines a Remote Authentication Dial
   In User Service (RADIUS) attribute that carries CE configuration
   information from the AAA server to the BNG.

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/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 7, 2017.

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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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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Configuration process with RADIUS . . . . . . . . . . . . . .   3
   4.  Attributes  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Softwire46-Configuration Attribute  . . . . . . . . . . .   6
     4.2.  S46 Container Options . . . . . . . . . . . . . . . . . .   7
     4.3.  Sub Options for S46 Container Option  . . . . . . . . . .   7
       4.3.1.  S46-Rule Sub Option . . . . . . . . . . . . . . . . .   7
       4.3.2.  S46-BR Sub Option . . . . . . . . . . . . . . . . . .   8
       4.3.3.  S46-DMR Sub Option  . . . . . . . . . . . . . . . . .   9
       4.3.4.  S46-V4V6Bind Sub Option . . . . . . . . . . . . . . .   9
       4.3.5.  S46-PORTPARAMS Sub Option . . . . . . . . . . . . . .  10
     4.4.  Sub Options for S46-RULE Sub Option . . . . . . . . . . .  11
       4.4.1.  Rule-IPv6-Prefix Sub Option . . . . . . . . . . . . .  11
       4.4.2.  Rule-IPv4-Prefix Sub Option . . . . . . . . . . . . .  12
       4.4.3.  EA Length Sub Option  . . . . . . . . . . . . . . . .  13
     4.5.  Softwire46 Sub Options Encapsulation  . . . . . . . . . .  13
     4.6.  Softwire46-Priority Attribute . . . . . . . . . . . . . .  13
     4.7.  Table of attributes . . . . . . . . . . . . . . . . . . .  14
   5.  Diameter Considerations . . . . . . . . . . . . . . . . . . .  15
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Additional Authors  . . . . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

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1.  Introduction

   Recently providers have started to deploy IPv6 and consider how to
   transit to IPv6.  Many transition mechanisms based on the Address
   plus Port (A+P) [RFC6346] have been proposed for running IPv4 over
   IPv6-only infrastructure, including MAP-E, MAP-T, and Lightweight
   4over6.  Mapping of Address and Port with Encapsulation(MAP-
   E)[RFC7597], Mapping of Address and Port with using Translation(MAP-
   T)[RFC7599] are stateless mechanisms for running IPv4 over IPv6-only
   infrastructure.  Lightweight 4over6[RFC7596] is a hub-and-spoke IPv4-
   over-IPv6 tunneling mechanism, with complete independence of IPv4 and
   IPv6 addressing.  They provide both IPv4 and IPv6 connectivity
   services simultaneously during the IPv4/IPv6 co-existing period.
   MAP-E, MAP-T and Lightweight 4over6 have adopted Dynamic Host
   Configuration Protocol for IPv6 (DHCPv6) [RFC3315] as auto-
   configuring protocol.  The Customer Edge (CE) uses DHCPv6 options to
   discover the Border Relay (BR) and get Softwire46 (S46)
   configurations.

   In many networks, user configuration information may be stored in the
   Authentication, Authorization, and Accounting (AAA) servers.  Current
   the AAA servers communicate using the Remote Authentication Dial In
   User Service (RADIUS) [RFC2865] protocol.  In a fixed line broadband
   network, the Broadband Network Gateways (BNGs) act as the access
   gateway of users.  The BNGs are assumed to embed a DHCPv6 server
   function that allows them to locally handle any DHCPv6 requests
   initiated by hosts.

   Since the S46 configuration information is stored in the AAA servers
   and user configuration is mainly transmitted through DHCPv6 protocol
   between the BNGs and hosts/CEs, new RADIUS attributes are needed to
   propagate the information from the AAA servers to the BNGs.  The
   RADIUS attributes designed in this document are especially for the
   MAP-E[RFC7597], MAP-T[RFC7599] and Lightweight 4over6[RFC7596],
   providing enough information to form the correspondent DHCPv6
   configuration options[RFC7598].

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Configuration process with RADIUS

   The below Figure 1 illustrates how the RADIUS protocol and DHCPv6 co-
   operate to provide CE with MAP configuration information.  The BNG
   acts as a RADIUS client and as a DHCPv6 server.

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         CE                         BNG                       AAA Server
         |                           |                               |
         |-----1.DHCPv6 Solicit----->|                               |
         | (ORO w/container option)  |                               |
         |                           |-------2.Access-Request------->|
         |                           | (S46-Configuration attriubte) |
         |                           |                               |
         |                           |<------3.Access-Accept---------|
         |<--4.DHCPv6 Advertisement--| (S46-Configuration attriubte) |
         |                           |                               |
         |-----5.DHCPv6  Request---->|                               |
         |    (container Option)     |                               |
         |<----6.DHCPv6 Reply--------|                               |
         |    (cointainer option)    |                               |
         |                           |                               |
                   DHCPv6                         RADIUS

    Figure 1: the cooperation between DHCPv6 and RADIUS combining with
                           RADIUS authentication

   1.  First, the CE MAY initiate a DHCPv6 Solicit message that includes
   an Option Request option(6) [RFC3315] with the S46 Container options
   as defined in[RFC7598].  OPTION_S46_CONT_MAPE should be included for
   MAP-E[RFC7597], OPTION_S46_CONT_MAPT for MAP-T[RFC7599], and
   OPTION_S46_CONT_LW for Lightweight 4over6[RFC7596].  Note however,
   that the ORO (Option Request option) with the S46 Container option
   code could be optional if the network was planned as S46-enabled as
   default.

   2.  When the BNG receives the SOLICIT, it should initiate the radius
   Access-Request message, in which the User-Name attribute (1) should
   be filled by the CE MAC address or interface-id or both, to the
   RADIUS server and the User-password attribute (2) should be filled by
   the shared password that has been preconfigured on the DHCPv6 server,
   requesting authentication as defined in [RFC2865] with the
   corresponding Softwire46-Configuration Attribute, which will be
   defined in the next Section.

   3.  If the authentication request is approved by the AAA server, an
   Access-Accept message MUST be acknowledged with the corresponding
   Softwire46-Configuration Attribute.

   4.  After receiving the Access-Accept message with the corresponding
   Attribute, the BNG SHOULD respond to the CE with an Advertisement
   message.

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   5.  After receiving the Advertise message, the CE MAY request for the
   corresponding S46 Container option, by including the S46 Container
   option in the Request Message.

   6.  After receiving the client's Request messsage, containing the
   corresponding S46 Container option the BNG SHOULD reply to the CE
   with the message containing the S46 Container option.  The
   recommended format of the MAC address is defined as Calling-Station-
   Id (Section 3.20 in [RFC3580] without the SSID (Service Set
   Identifier) portion.

   For Lightweight 4over6 [RFC7596], the subscriber's binding state
   should be synchronized between the AAA server and the lwAFTR.  If the
   bindings are pre-configured statically, in both the AAA server and
   the lwAFTR, the AAA server does not need to configure the lwAFTR
   anymore.  Otherwise, if the bindings are locally created on-demand in
   the AAA server, it should inform the lwAFTR with the subscriber's
   binding state, in order to synchronise the binding information of the
   lwB4 with the lwAFTR.

   The authorization operation could also be done independently after
   the authentication process.  In such a scenario, after the
   authentication operation, the client MAY initiate a DHCPv6 Request
   message that includes the corresponding S46 Container options.
   Similar to the above scenario, the ORO with the corresponding S46
   Container option code in the initial DHCPv6 request could be optional
   if the network was planned as being S46-enabled vy default.  When the
   BNG receives the DHCPv6 Request, it SHOULD initiate the radius
   Access-Request message, which MUST contain 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].  If
   the authorization request is approved by the AAA server, an Access-
   Accept message MUST be acknowledged with the corresponding
   Softwire46-Configuration Attribute.  The BNG SHOULD then send the
   DHCPv6 Reply message containing the S46 Container option.

   In both the above-mentioned scenarios, 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 MAP-Configuration
   Attribute in the Access-Accept it MAY fallback to a pre-configured
   default S46 configuration, if any.  If the BNG does not have any pre-
   configured default S46 configuration, or if the BNG receives an
   Access-Reject, then S46 cannot be established.

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   As specified in [RFC3315], section 18.1.4, "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, the secondary BNG receiving
   the DHCPv6 message MUST initiate a new Access-Request towards the AAA
   server.  The secondary BNG MAY include the MAP-Configuration
   Attribute in its Access-Request.

4.  Attributes

   This section defines the Softwire46-Configuration Attribute and the
   Softwire46-Priority Attribute.  The attribute design follows
   [RFC6158] and refers to [RFC6929].  The Softwire46-Configuration
   Attribute carries the configuration information for MAP-E, MAP-T, and
   Lightweight 4over6.  The configuration information for each S46
   mechanism is carried in the corresponding S46 Container option.
   Different sub options are required for each type of S46 Container
   option.  The RADIUS attribute for Dual-Stack Lite [RFC6333] is
   defined in [RFC6519].

   A client may be capable of supporting several different S46
   mechanisms.  Depending on the deployment scenario, a client might
   request for more than one S46 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].

4.1.  Softwire46-Configuration Attribute

   The Softwire46-Configuration Attribute is structured as follows:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |    Length     |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
|                                                               |
+                    S46 Container Option(s)                    +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Type
    TBD
  Length
    2 + the length of the S46 Container option(s) specified in octects
  S46 Container Option (s)
    A variable field that may contains one or more S46 Container option(s),
    defined in Section 4.2

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4.2.  S46 Container Options

   Depending on the deployment scenario, a client might request for more
   than one transition mechanism at a time, at least one S46 Container
   option MUST be included in one Softwire46-Configuration Attribute.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |    Length     |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                         Sub Options                           +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Type
        1 MAP-E Container Option
        2 MAP-T Container Option
        3 Lightweight 4over6 Container Option
      Length
        2 + the length of the sub options specified in octects
      Sub Option
        A variable field that contains necessary sub options defined in
        Section 4.3 and zero or several optional sub options, defined
        in Section 4.4.

4.3.  Sub Options for S46 Container Option

4.3.1.  S46-Rule Sub Option

   Depending on deployment scenario, one Basic Mapping Rule and zero or
   more Forwarding Mapping Rules MUST be included in one MAP-E or MAP-T
   Container Option.

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     SubType   |    SubLen     |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                         Sub Options                           +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      SubType
        1 Basic Mapping Rule (Not Forwarding Mapping Rule)
        2 Forwarding Mapping Rule (Not Basic Mapping Rule)
        3 Basic & Forwarding Mapping Rule
      SubLen
        2 + the length of the sub options specified in octects
      Sub Option
        A variable field that contains sub options defined in
        Section 4.4

4.3.2.  S46-BR Sub Option

   There MUST be atleast one S46-BR Sub Option included in each MAP-E
   Container Option or Lightweight 4over6 Container Option.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    SubType    |    SubLen     |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
|                                                               |
|                        BR-ipv6-address                        |
|                                                               |
+                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   SubType
      4 (SubType number, for the S46-BR sub option)
   SubLen
      18 (the length of the S46-BR sub option)
   BR-ipv6-address
      a fixed-length field of 16 octects that specifies the IPv6 address
      for the S46 BR.

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4.3.3.  S46-DMR Sub Option

   There MUST be exactly one S46-DMR Sub Option included in one MAP-T
   Container Option.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    SubType    |    SubLen     |dmr-prefix6-len|               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
|                        dmr-ipv6-prefix                        |
|                       (variable length)                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   SubType
      5 (SubType number, for the S46-DMR sub option)
   SubLen
      3 + length of dmr-ipv6-prefix specified in octects
   dmr-prefix6-len
      8 bits longs; expresses the bitmask length of the IPv6
      prefix specified in the dmr-ipv6-prefix field. Allowed values range
      from 0-96.
   dmr-ipv6-prefix
      a variable-length field specifying the IPv6 prefix or address
      for the BR. This field is right-padded with zeros to the nearest
      octect boundary when dmr-prefix6-len is not divisible by 8.

4.3.4.  S46-V4V6Bind Sub Option

   There MUST be atmost one S46-V4V6Bind Sub Option included in each
   Lightweight 4over6 Container Option.

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 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    SubType    |    SubLen     |         ipv4-address          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          (Continued)          |bindprefix6-len|               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
|                        bind-ipv6-prefix                       |
|                        (variable length)                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   SubType
      6 (SubType number, for the S46-V4V6Bind sub option)
   SubLen
      the length of the S46-V4V6Bind sub option expressed in octects
   ipv4-address
      a 32-bits field that specifies an IPv4 address that appears in
      the V4V6Bind Option
   bindprefix6-len
      8 bits long; expresses the bitmask length of the IPv6 prefix
      specified in the bind-ipv6-prefix field. Allowed values range from
      0 to 96.
   bind-ipv6-prefix
      a variable-length field specifying the IPv6 prefix or address for
      the S46 CE. This field is right-padded with zeros to the nearest octect
      boundary when bindprefix6-len is not divisible by 8.

4.3.5.  S46-PORTPARAMS Sub Option

   The S46-PORTPARAMS sub option specifies optional port set information
   that MAY be provided to CEs.  The S46-PORTPARAMS sub option canbe
   included optionally by each type of S46 Container Option.

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 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    SubType    |    SubLen     |  PSID-Offset  |   PSID-len    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              PSID             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   SubType
      7 (SubType number, for the S46-PORTPARAMS Sub Option sub option)
   SubLen
      6 (the length of the S46-PORTPARAMS Sub Option sub option)
   PSID Offset
      8 bits long field that specifies the numeric value for the S46 algorithm's excluded
      port range/ offset bits (a bits), as per Section 5.1 of RFC 7597.
      Allowed values are between 0 and 15. Default values for this field are specific to the
      Softwire mechanism being implemented and are defined in the relevant specification document.
   PSID-len
      8 bits long; 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 valid of PSID. Subsequently, the
      address sharing ratio would be 2 ^k.
   PSID (Port-set ID)
      Explicit 16-bit (unsigned word) PSID value.  The PSID value
      algorithmically identifies a set of ports assigned to a CE. The
      first k-bits on the left of this 2-octets field is the PSID
      value. The remaining (16-k) bits on the right are padding zeros.

4.4.  Sub Options for S46-RULE Sub Option

4.4.1.  Rule-IPv6-Prefix Sub Option

   The Rule-IPv6-Prefix Sub Option is necessary for every S46-RULE sub
   option.  It should appear for once and only once.

   The IPv6 Prefix sub option is followed the framed IPv6 prefix
   designed in [RFC3162].

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    SubType    |    SubLen     |   Reserved    |  prefix6-len  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        rule-ipv6-prefix                       |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      SubType
         9 (SubType number, for the Rule-IPv6-Prefix6 sub option)
      SubLen
         20 (the length of the Rule-IPv6-Prefix6 sub option)
      Reserved
         Reserved for future usage. It should be set to all zero
      prefix6-len
         length of the IPv6 prefix, specified in the rule-ipv6-prefix
         field, expressed in bits
      rule-ipv6-prefix
         a 128-bits field that specifies an IPv6 prefix that appears in
         a MAP rule

4.4.2.  Rule-IPv4-Prefix Sub Option

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    SubType    |    SubLen     |   Reserved    |  prefix4-len  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       rule-ipv4-prefix                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      SubType
         10 (SubType number, for the Rule-IPv4-Prefix6 sub option)
      SubLen
         8 (the length of the Rule-IPv4-Prefix6 sub option)
      Reserved
         Reserved for future usage. It should be set to all zero
      Prefix4-len
         length of the IPv6 prefix, specified in the rule-ipv6-prefix
         field, expressed in bits
      rule-ipv4-prefix
         a 32-bits field that specifies an IPv4 prefix that appears in
         a MAP rule

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4.4.3.  EA Length Sub Option

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    SubType    |    SubLen     |             EA-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      SubType
         11 (SubType number, for the EA Length sub option)
      SubLen
         4 (the length of the EA Length sub option)
      EA-len
         16 bits long field that specifies the Embedded-Address (EA)
         bit length.  Allowed values range from 0 to 48

4.5.  Softwire46 Sub Options Encapsulation

   The table below shows which encapsulated Sub Options are mandatory,
   optional, or not permitted for each defined S46 Container Option.

   +----------------+-------+-------+--------------------+
   | Sub Option     | MAP-E | MAP-T | Lightweight 4over6 |
   +----------------+-------+-------+--------------------+
   | S46-BR         |   M   |  N/P  |          M         |
   +----------------+-------+-------+--------------------+
   | S46-Rule       |   M   |   M   |         N/P        |
   +----------------+-------+-------+--------------------+
   | S46-DMR        |  N/P  |   M   |         N/P        |
   +----------------+-------+-------+--------------------+
   | S46-V4V6Bind   |  N/P  |  N/P  |          O         |
   +----------------+-------+-------+--------------------+
   | S46-PORTPARAMS |   O   |   O   |          O         |
   +----------------+-------+-------+--------------------+
   | S46-Option-Code|  N/P  |  N/P  |         N/P        |
   +----------------+-------+-------+--------------------+

   M - Maandabdatory, O - Optional, N/P - Not Permitted

4.6.  Softwire46-Priority Attribute

   The S46-Priority Attribute is structured as follows:

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 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |    Length     |       S46-option-code         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             ...               |       S46-option-code         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
      TBD
   Length
      2 + the length of the S46-option-code(s) specified in octects
   S46-option-code
      16-bit IANA-registered option code of the DHCPv6 option that is used to identify the
      softwire mechanisms. S46 mechanisms are prioritized in the appearance order of the
      S46-option-code(s) in the Softwire46-Priority Attribute. A Softwire46-Priority Attribute
      MUST contain at least one S46-option-code.

4.7.  Table of attributes

   The following table provides a guide to which attributes may be found
   in which kinds of packets, and in what quantity.

   Request Accept Reject Challenge Accounting  #  Attribute
                                    Request
    0-1     0-1     0      0         0-1      TBD1 Softwire46-
                                                   Configuration
    0-1     0-1     0      0         0-1      TBD2 Softwire46-
                                                   Priority
    0-1     0-1     0      0         0-1      1    User-Name
    0-1     0       0      0         0        2    User-Password
    0-1     0-1     0      0         0-1      6    Service-Type
    0-1     0-1     0-1    0-1       0-1      80   Message-Authenticator

   The following table defines the meaning of the above table entries.

   0     This attribute MUST NOT be present in packet.
   0+    Zero or more instances of this attribute MAY be present in
         packet.
   0-1   Zero or one instance of this attribute MAY be present in
         packet.
   1     Exactly one instance of this attribute MUST be present in
         packet.

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5.  Diameter Considerations

   S46 Configuration using Diameter [RFC6733] is specified in [RFC7678].

6.  IANA Considerations

   This document requires the assignment of two new RADIUS Attributes
   Type in the "Radius Types" registry (currently located at
   http://www.iana.org/assignments/radius-types for the following
   attributes:

   o  Softwire46-Configuration Attribute TBD1

   o  Softwire46-Priority Attribute TBD2

   IANA should allocate the numbers from the standard RADIUS Attributes
   space using the "IETF Review" policy [RFC5226].

7.  Security Considerations

   Known security vulnerabilities of the RADIUS protocol are discussed
   in [RFC2607], [RFC2865], and[RFC2869].  Use of IPsec [RFC4301] for
   providing security when RADIUS is carried in IPv6 is discussed in
   [RFC3162].

   A malicious user may use MAC address spoofing on the shared password
   that has been preconfigured on the DHCPv6 server to get unauthorized
   configuration information.

   Security considerations for MAP specific between the MAP CE and the
   BNG are discussed in [RFC7597].  Security considerations for
   Lightweight 4over6 are discussed in [RFC7596].  Security
   considerations for DHCPv6-Based S46 Prioritization Mechanism are
   discussed in [RFC8026].  Furthermore, generic DHCPv6 security
   mechanisms can be applied DHCPv6 intercommunication between the CE
   and the BNG.

   Security considerations for the Diameter protocol are discussed in
   [RFC6733].

8.  Acknowledgements

   The authors would like to thank the valuable comments made by Peter
   Lothberg, Wojciech Dec, and Suresh Krishnan for this document.  This
   document was merged with draft-sun-softwire-lw4over6-radext-01,
   thanks to everyone who contributed to this draft.

   This document was produced using the xml2rfc tool [RFC7749].

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9.  References

9.1.  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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc2865>.

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

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

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3580]  Congdon, P., Aboba, B., Smith, A., Zorn, G., and J. Roese,
              "IEEE 802.1X Remote Authentication Dial In User Service
              (RADIUS) Usage Guidelines", RFC 3580,
              DOI 10.17487/RFC3580, September 2003,
              <http://www.rfc-editor.org/info/rfc3580>.

   [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, <http://www.rfc-editor.org/info/rfc5080>.

   [RFC6158]  DeKok, A., Ed. and G. Weber, "RADIUS Design Guidelines",
              BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6929>.

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   [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, <http://www.rfc-editor.org/info/rfc8026>.

9.2.  Informative References

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

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

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [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>.

   [RFC6346]  Bush, R., Ed., "The Address plus Port (A+P) Approach to
              the IPv4 Address Shortage", RFC 6346,
              DOI 10.17487/RFC6346, August 2011,
              <http://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, <http://www.rfc-editor.org/info/rfc6519>.

   [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,
              <http://www.rfc-editor.org/info/rfc6733>.

   [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, <http://www.rfc-editor.org/info/rfc7596>.

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   [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,
              <http://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,
              <http://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, <http://www.rfc-editor.org/info/rfc7599>.

   [RFC7678]  Zhou, C., Taylor, T., Sun, Q., and M. Boucadair,
              "Attribute-Value Pairs for Provisioning Customer Equipment
              Supporting IPv4-Over-IPv6 Transitional Solutions",
              RFC 7678, DOI 10.17487/RFC7678, October 2015,
              <http://www.rfc-editor.org/info/rfc7678>.

   [RFC7749]  Reschke, J., "The "xml2rfc" Version 2 Vocabulary",
              RFC 7749, DOI 10.17487/RFC7749, February 2016,
              <http://www.rfc-editor.org/info/rfc7749>.

Additional Authors

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   Qiong Sun
   China Telecom
   Beijing  China
   Email: sunqiong@ctbri.com.cn

   Qi Sun
   Tsinghua University
   Department of Computer Science, Tsinghua University
   Beijing 100084
   P.R.China
   Phone: +86-10-6278-5822
   Email: sunqibupt@gmail.com

   Cathy Zhou
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen 518129
   Email: cathy.zhou@huawei.com

   Tina Tsou
   Huawei Technologies(USA)
   2330 Central Expressway
   Santa Clara, CA 95050
   USA
   Email: Tina.Tsou.Zouting@huawei.com

   ZiLong Liu
   Tsinghua University
   Beijing 100084
   P.R.China
   Phone: +86-10-6278-5822
   Email: liuzilong8266@126.com

   Yong Cui
   Tsinghua University
   Beijing 100084
   P.R.China
   Phone: +86-10-62603059
   Email: yong@csnet1.cs.tsinghua.edu.cn

Authors' Addresses

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

   Email: jiangsheng@huawei.com

   Yu Fu
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Hai-Dian District, Beijing, 100190
   P.R. China

   Email: fuyu@cnnic.cn

   Bing Liu
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   P.R. China

   Email: leo.liubing@huawei.com

   Peter Deacon
   IEA Software, Inc.
   P.O. Box 1170
   Veradale, WA  99037
   USA

   Email: peterd@iea-software.com

   Chongfeng Xie
   China Telecom
   Beijing
   P.R. China

   Email: xiechf@ctbri.com.cn

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   Tianxiang Li
   Tsinghua University
   Beijing  100084
   P.R.China

   Email: peter416733@gmail.com

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