RFC 8658 PROPOSED STANDARD RADIUS · IPV6 TRANSITION · SOFTWIRES
RADIUS for A+P softwires: RADIUS Attributes for Softwire Mechanisms Based on Address plus Port (A+P)
New RADIUS attributes that let an AAA server hand IPv4-over-IPv6 softwire settings to a broadband gateway.
RFC EDITOR
Jiang, S., Ed., Fu, Y., Ed., Xie, C., Li, T., and M. Boucadair, Ed., "RADIUS Attributes for Softwire Mechanisms Based on Address plus Port (A+P)", RFC 8658, DOI 10.17487/RFC8658, November 2019, <https://www.rfc-editor.org/info/rfc8658>.
BIBTEX
@misc{rfc8658,
series = {Request for Comments},
number = 8658,
howpublished = {RFC 8658},
publisher = {RFC Editor},
doi = {10.17487/RFC8658},
url = {https://www.rfc-editor.org/info/rfc8658},
author = {S. Jiang and Y. Fu and C. Xie and T. Li and M. Boucadair},
title = {{RADIUS Attributes for Softwire Mechanisms Based on Address plus Port (A+P)}},
pagetotal = 34,
year = 2019,
month = nov,
} RFC text
Contents
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
AI ELI5
On this page
PROBLEMProviders moving to IPv6 use A+P softwire mechanisms (MAP-E, MAP-T, Lightweight 4over6) to keep IPv4 working, and DHCPv6 options exist to configure clients. But in many networks the subscriber configuration lives in an AAA server that speaks RADIUS, which had no way to carry these settings.
MECHANISMThe RFC defines three extended RADIUS attributes, Softwire46-Configuration (241.9), Softwire46-Priority (241.10) and Softwire46-Multicast (241.11), whose nested fields map one to one onto the DHCPv6 options. The Broadband Network Gateway reads them from the AAA server and uses them to fill in the DHCPv6 options it sends to the customer device.
WHY IT MATTERSOperators can store softwire configuration centrally in their AAA server and have it flow to customer devices through the existing DHCPv6 exchange, for unicast and multicast alike.
§1Why RADIUS Needs Softwire Attributes
Providers are moving to IPv6, and several IPv4 service continuity mechanisms based on Address plus Port (A+P, RFC 6346) carry IPv4 over an IPv6-only network. They are MAP-E (RFC 7597), MAP-T (RFC 7599) and Lightweight 4over6 (RFC 7596). RFC 8114 adds delivery of IPv4 multicast over an IPv6 multicast network. For each of these, DHCPv6 options already exist to configure the client.
In many networks, though, user configuration is kept in an Authentication, Authorization, and Accounting (AAA) server that talks RADIUS. In fixed broadband, the Broadband Network Gateway (BNG) is both a AAA client and the DHCPv6 server for the customer device (the CE). New RADIUS attributes are needed to carry the settings from the AAA server to the BNG so it can pass them on in DHCPv6.
The contents of the new attributes map 1:1 onto the fields of the DHCPv6 options in RFC 7598, RFC 8026 and RFC 8115. The RFC targets deployments where a trusted relationship exists between the RADIUS client and server.
The provider keeps each customer's settings in one big list. This RFC teaches that list how to pass along the special settings, so the gateway can then hand them to your home router.
§3.1The Softwire46-Configuration Attribute
The unicast settings travel in Softwire46-Configuration, a tlv-type attribute with Type 241 and Extended-Type 9, written 241.9. Inside it sits one or more of three attributes: Softwire46-MAP-E (TLV-Type 1), Softwire46-MAP-T (2) and Softwire46-Lightweight-4over6 (3). Each may appear at most once, and at least one MUST be present. The BNG SHALL use them to populate the DHCPv6 Softwire46 container options defined in RFC 7598.
Each mechanism requires a different set of sub-attributes. MAP-E needs one rule and at least one border relay address (Softwire46-BR). MAP-T needs one rule and exactly one default mapping rule (Softwire46-DMR). Lightweight 4over6 needs at least one BR and one Softwire46-V4V6Bind. All three MAY carry one Softwire46-PORTPARAMS.
The attribute MAY appear in an Access-Accept, and in an Access-Request to indicate a preferred configuration, though the server need not honor that preference. It MAY also appear in CoA-Request and Accounting-Request packets, and MUST NOT appear in any other RADIUS packet.
It is a labeled box with a few smaller boxes inside. Which small boxes you must include depends on which kind of translation trick the customer uses.
- Softwire46-Configuration 241.9
- Softwire46-MAP-E
- Softwire46-Rule
- Softwire46-BR
- Softwire46-PORTPARAMS
- Softwire46-MAP-T
- Softwire46-Rule
- Softwire46-DMR
- Softwire46-PORTPARAMS
- Softwire46-Lightweight-4over6
- Softwire46-BR
- Softwire46-V4V6Bind
- Softwire46-PORTPARAMS
- Softwire46-MAP-E
| Sub-attribute | 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 |
§3.1.3Rules, Relays and Port Sets
Softwire46-Rule comes in two kinds: TLV-Type 4 is the Basic Mapping Rule (not to be used for forwarding) and TLV-Type 5 is a Forwarding Permitted Mapping Rule. Using type 5 is equivalent to setting the F flag in the DHCPv6 OPTION_S46_RULE. A rule holds Rule-IPv6-Prefix (10), Rule-IPv4-Prefix (11) and EA-Length (12), where the Embedded Address length ranges from 0 to 48.
Softwire46-BR (6) is a single IPv6 address of 16 octets for the Border Relay. Softwire46-DMR (7) is an IPv6 prefix, with allowed lengths from 0 to 96. Softwire46-V4V6Bind (8) pairs an IPv4-Address (13), the full or shared IPv4 address of the CE, with a Bind-IPv6-Prefix (14) that tells the CE which prefix to use as the tunnel source.
Softwire46-PORTPARAMS (9) describes how an IPv4 address is shared between clients. It holds PSID-Offset (15), PSID-Len (16) and PSID (17). When PSID-Len is 0 the PSID field is ignored, and the address-sharing ratio is 2^k for a PSID length of k bits. Each of these is encoded in 32 bits, with the value right justified and unused bits set to zero.
Sharing one street address among many families means each family gets its own set of door numbers. These small pieces say which rule to follow, which relay to use and which door numbers belong to you.
§3.2Priority and Multicast Attributes
A client may support several mechanisms and request more than one. Softwire46-Priority (241.10) carries an ordered list of Softwire46-Option-Code TLVs (type 18), and the first one listed is the most preferred. It corresponds to OPTION_S46_PRIORITY in RFC 8026. At least one option code MUST be present. The initial codes are 1 for MAP-E, 2 for MAP-T, 3 for Lightweight 4over6 and 144 for DS-Lite.
Softwire46-Multicast (241.11) carries the IPv6 prefixes used to build IPv4-embedded IPv6 addresses as in RFC 8114, and the BNG uses them to fill the DHCPv6 PREFIX64 option. It must include ASM-Prefix64 (19) or SSM-Prefix64 (20), or both. Both have to be a /96 prefix in the right multicast range. U-Prefix64 (21) MUST be present when SSM-Prefix64 is, and MAY be present with ASM-Prefix64. Its length MUST be 32, 40, 48, 56, 64 or 96.
If a home router knows several tricks, the provider can list them in order of favorite. Another box holds the special addresses used for TV-style streams sent to many viewers at once.
§4How RADIUS and DHCPv6 Work Together
The CE sends a DHCPv6 Solicit that asks for a softwire container option: OPTION_S46_CONT_MAPE (94) for MAP-E, OPTION_S46_CONT_MAPT (95) for MAP-T, OPTION_S46_CONT_LW (96) for Lightweight 4over6, or option 113 for multicast. The BNG then sends a RADIUS Access-Request, with a User-Name and User-Password and the matching Softwire46 attribute. If the AAA server authenticates the request and has a suitable configuration, it returns an Access-Accept with the attributes. The BNG maps them into DHCPv6 options, and the CE gets them in the Advertise and Reply messages.
Authorization can be done separately, using an Access-Request with Service-Type 'Authorize Only' (17) and a State attribute. If the BNG gets no softwire attribute back, it may fall back to a preconfigured configuration. If it gets an Access-Reject, it must not supply the configuration to the client.
When configuration changes, such as a new BR address, the AAA server can send a CoA-Request. The BNG then sends a DHCPv6 Reconfigure to the CE, which responds with a Renew or Information-Request to fetch the update. For Lightweight 4over6, the CE binding state must also be synchronized with the lwAFTR/BR, either by static preconfiguration or on demand by the AAA server.
Your router asks the gateway for its settings. The gateway checks the guest list, gets the answer, and passes it back. If the list changes later, the gateway taps your router on the shoulder to ask it to check again.
CEBNGAAA Server
- DHCPv6 SolicitAsks for softwire container option(s).
- Access-RequestCarries Softwire46 attribute(s).
- Access-AcceptReturns the configuration.
- DHCPv6 AdvertiseContainer option(s) filled from the attributes.
- DHCPv6 Request
- DHCPv6 Reply
§6Security Considerations
The RFC says it introduces no security issues inherently different from those in RFC 2865 and, for CoA messages, RFC 5176. The known weaknesses of RADIUS apply, and they impose a requirement to trust the counterparty. For that reason the document targets deployments with a trusted relationship between RADIUS client and server, with communication optionally secured by IPsec or TLS.
The sample process also advises that the Message-Authenticator attribute (type 80) should be used to protect both Access-Request and Access-Accept messages. Security issues of each softwire mechanism, and of the DHCPv6 side between CE and BNG, are left to the RFCs that define them.
The provider's gateway and its guest list have to trust each other, because the list is only as safe as the link between them. The RFC says to protect that link.
§7IANA Registrations
IANA assigned three attributes from the Short Extended Space of RFC 6929: 241.9 Softwire46-Configuration, 241.10 Softwire46-Priority and 241.11 Softwire46-Multicast, all of data type tlv.
IANA also created a registry called 'RADIUS Softwire46 Configuration and Multicast Attributes', holding the nested values 1 to 21 with 0 reserved and 22-255 unassigned. New entries need Standards Action. A second registry, 'Option Codes Permitted in the Softwire46-Priority Attribute', lists the codes for each mechanism, and new codes can be added through IETF Review.
The numbers for the new labels were written in the official phone book of RADIUS, so everyone uses the same ones.
- 1MAP-E — Defined in RFC 7597.
- 2MAP-T — Defined in RFC 7599.
- 3Lightweight 4over6 — Defined in RFC 7596.
- 144DS-Lite — Derived from the RADIUS attribute type for DS-Lite in RFC 6519.
§8References
[RFC2865]RFC 2865Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000.June 2000[RFC6929]RFC 6929DeKok, A. and A. Lior, "Remote Authentication Dial In User Service (RADIUS) Protocol Extensions", RFC 6929, April 2013.April 2013[RFC7596]RFC 7596Lightweight 4over6: An Extension to the Dual-Stack Lite Architecture, RFC 7596.July 2015[RFC7597]RFC 7597Mapping of Address and Port with Encapsulation (MAP-E), RFC 7597.July 2015[RFC7598]RFC 7598DHCPv6 options for the configuration of Softwire46 address and port-mapped clients, RFC 7598.July 2015[RFC7599]RFC 7599Mapping of Address and Port using Translation (MAP-T), RFC 7599.July 2015[RFC8026]RFC 8026Boucadair, M. and I. Farrer, "Unified IPv4-in-IPv6 Softwire Customer Premises Equipment (CPE): A DHCPv6-Based Prioritization Mechanism", RFC 8026, November 2016.November 2016[RFC8044]RFC 8044DeKok, A., "Data Types in RADIUS", RFC 8044, January 2017.January 2017[RFC8114]RFC 8114Delivery of IPv4 Multicast Services to IPv4 Clients over an IPv6 Multicast Network, RFC 8114.March 2017[RFC8115]RFC 8115Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6 Option for IPv4-Embedded Multicast and Unicast IPv6 Prefixes", RFC 8115, March 2017.March 2017[RFC6346]RFC 6346Bush, R., Ed., "The Address plus Port (A+P) Approach to the IPv4 Address Shortage", RFC 6346, August 2011.August 2011[RFC6519]RFC 6519RADIUS Extensions for Dual-Stack Lite, RFC 6519.February 2012