softwire R. Maglione
Internet-Draft Telecom Italia
Intended status: Standards Track A. Durand
Expires: February 11, 2012 Juniper Networks
August 10, 2011
RADIUS Extensions for Dual-Stack Lite
draft-ietf-softwire-dslite-radius-ext-05
Abstract
Dual-Stack Lite is a solution to offer both IPv4 and IPv6
connectivity to customers which are addressed only with an IPv6
prefix. Dual-Stack Lite requires to pre-configure the Dual-Stack
Lite Address Family Transition Router (AFTR) tunnel information on
the Basic Bridging BroadBand (B4) element. In many networks, the
customer profile information may be stored in Authentication
Authorization and Accounting (AAA) servers while client
configurations are mainly provided through Dynamic Host Configuration
Protocol (DHCP). This document specifies a new Remote Authentication
Dial In User Service (RADIUS) attribute to carry Dual-Stack Lite
Address Family Transition Router Tunnel name; the RADIUS attribute is
defined based on the equivalent DHCPv6 OPTION_AFTR_NAME option. This
RADIUS attribute is meant to be used between the RADIUS Server and
the Network Access Server (NAS), it is not intended to be used
directly between the Basic Bridging BroadBand element and the RADIUS
Server.
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
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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 February 11, 2012.
Copyright Notice
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Internet-Draft DS-Lite RADIUS Extensions August 2011
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. DS-Lite Configuration with RADIUS and DHCPv6 . . . . . . . . . 5
4. RADIUS Attribute . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. DS-Lite-Tunnel-Name . . . . . . . . . . . . . . . . . . . 8
5. Table of attributes . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Dual-Stack Lite [RFC6333] is a solution to offer both IPv4 and IPv6
connectivity to customers which are addressed only with an IPv6
prefix (no IPv4 address is assigned to the attachment device). One
of its key components is an IPv4-over-IPv6 tunnel, but a Dual-Stack-
Lite Basic Bridging BroadBand (B4) will not know if the network it is
attached to offers Dual-Stack Lite support, and if it did, would not
know the remote end of the tunnel to establish a connection.
To inform the Basic Bridging BroadBand (B4) of the Address Family
Transition Router's (AFTR) location, a Fully Qualified Domain Name
(FQDN) may be used. Once this information is conveyed, the presence
of the configuration indicating the AFTR's location also informs a
host to initiate Dual-Stack Lite (DS-Lite) service and become a
Softwire Initiator.
[RFC6334] specifies a DHCPv6 option which is meant to be used by a
Dual-Stack Lite client (Basic Bridging BroadBand element, B4) to
discover its Address Family Transition Router (AFTR) name. In order
to be able to populate such option the DHCPv6 Server must be pre-
provisioned with the Address Family Transition Router (AFTR) name.
In Broadband environments, customer profile may be managed by AAA
servers, together with user Authentication, Authorization, and
Accounting (AAA). Remote Authentication Dial In User Service
(RADIUS) protocol [RFC2865] is usually used by AAA Servers to
communicate with network elements. [I-D.ietf-radext-ipv6-access]
describes a typical broadband network scenario in which the Network
Access Server (NAS) acts as the access gateway for the users (hosts
or CPEs) and the NAS embeds a DHCPv6 Server function that allows it
to locally handle any DHCPv6 requests issued by the clients.
Since the DS-Lite AFTR information can be stored in AAA servers and
the client configuration is mainly provided through Dynamic Host
Configuration Protocol (DHCP) running between the NAS and the
requesting clients, a new RADIUS attribute is needed to send AFTR
information from AAA server to the NAS.
This document aims at defining a new RADIUS attribute to be used for
carrying the DS-Lite Tunnel Name, based on the equivalent DHCPv6
option already specified in [RFC6334]
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [RFC2119].
The terms DS-Lite Basic Bridging BroadBand element (B4) and the DS-
Lite Address Family Transition Router element (AFTR) are defined in
[RFC6333]
3. DS-Lite Configuration with RADIUS and DHCPv6
The Figure 1 illustrates how the RADIUS protocol and DHCPv6 work
together to accomplish DS-Lite configuration on the B4 element when a
PPP Session is used to provide connectivity to the user.
The Network Access Server (NAS) operates as a client of RADIUS and as
DHCP Server for DHC protocol. The NAS initially sends a RADIUS
Access Request message to the RADIUS server, requesting
authentication. Once the RADIUS server receives the request, it
validates the sending client and if the request is approved, the AAA
server replies with an Access Accept message including a list of
attribute-value pairs that describe the parameters to be used for
this session. This list may also contain the AFTR Tunnel Name. When
the NAS receives a DHCPv6 client request containing the DS-Lite
tunnel Option, the NAS shall use the name returned in the RADIUS DS-
Lite-Tunnel-Name attribute to populate the DHCPv6 OPTION_AFTR_NAME
option in the DHCPv6 reply message.
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B4 NAS AAA
| | Server
| | |
|----PPP LCP Config Request------> | |
| | |
| |----Access-Request ---->|
| | |
| |<---- Access-Accept-----|
| | (DS-Lite-Tunnel-Name) |
|<-----PPP LCP Config ACK ----- | |
| | |
| | |
|------ PPP IPv6CP Config Req ---->| |
| | |
|<----- PPP IPv6CP Config ACK -----| |
| | |
|------- DHCPv6 Solicit -------->| |
| | |
|<-------DHCPv6 Advertisement -----| |
| (DHCPv6 OPTION_AFTR_NAME) | |
| | |
|------- DHCPv6 Request -------->| |
| | |
|<-------- DHCPv6 Reply --------- | |
| (DHCPv6 OPTION_AFTR_NAME) | |
DHCPv6 RADIUS
Figure 1: RADIUS and DHCPv6 Message Flow for a PPP Session
The Figure 2 illustrates how the RADIUS protocol and DHCPv6 work
together to accomplish DS-Lite configuration on the B4 element when
an IP Session is used to provide connectivity to the user.
The only difference between this message flow and previous one is
that in this scenario the interaction between NAS and AAA/ RADIUS
Server is triggered by the DHCPv6 Solicit message received by the NAS
from the B4 acting as DHCPv6 client, while in case of a PPP Session
the trigger is the PPP LCP Config Request message received by the
NAS.
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B4 NAS AAA
| | Server
|------ DHCPv6 Solicit ---------> | |
| | |
| |----Access-Request ---->|
| | |
| |<-Access-Accept---------|
| | (DS-Lite-Tunnel-Name) |
| | |
|<-------DHCPv6 Advertisement------| |
| (DHCPv6 OPTION_AFTR_NAME) | |
| | |
|------- DHCPv6 Request -------->| |
| | |
| | |
| <---- DHCPv6 Reply ---- | |
| (DHCPv6 OPTION_AFTR_NAME) | |
DHCPv6 RADIUS
Figure 2: RADIUS and DHCPv6 Message Flow for an IP Session
After receiving the DS-Lite-Tunnel-Name in the initial Access-Accept
the NAS MUST store the received AFTR Tunnel Name locally. When the
B4 sends a DHCPv6 Renew message to request an extension of the
lifetimes for the assigned address or prefix, the NAS does not have
to initiate a new Access-Request towards the AAA server to request
the AFTR tunnel name. The NAS retrieves the previously stored AFTR
tunnel name and uses it in its reply.
According to [RFC3315] if the DHCPv6 server to which the DHCPv6 Renew
message was sent at time T1 has not responded, the DHCPv6 client
initiates a Rebind/Reply message exchange with any available server.
In this scenario the NAS receiving the DHCPv6 rebind message MUST
initiate a new Access-Request towards the AAA server. The NAS MAY
include the DS-Lite-Tunnel-Name attribute in its Access-Request.
If the NAS does not receive the DS-Lite-Tunnel-Name attribute in the
Access-Accept it MAY fallback to a pre-configured default tunnel
name, if any. If the NAS does not have any pre-configured default
tunnel name or if the NAS receives an Access-Reject, the tunnel
cannot be established and NAS MUST terminate the session towards the
B4.
4. RADIUS Attribute
This section specifies the format of the new RADIUS attribute.
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4.1. DS-Lite-Tunnel-Name
Description
The DS-Lite-Tunnel-Name RADIUS attribute contains a Fully Qualified
Domain Name that refers to the AFTR the client is requested to
establish a connection with. The NAS SHALL use the name returned in
the RADIUS DS-Lite-Tunnel-Name attribute to populate the DHCPv6
OPTION_AFTR_NAME option [RFC6334]
This attribute MAY be used in Access-Request packets as a hint to the
RADIUS server; for example if the NAS is pre-configured with a
default tunnel name, this name MAY be inserted in the attribute. The
RADIUS server MAY ignore the hint sent by the NAS and it MAY assign a
different AFTR tunnel name.
If the NAS includes the DS-Lite-Tunnel-Name attribute, but the AAA
server does not recognize it, this attribute MUST be ignored by the
AAA Server.
If the NAS does not receive DS-Lite-Tunnel-Name attribute in the
Access-Accept it MAY fallback to a pre-configured default tunnel
name, if any. If the NAS does not have any pre-configured default
tunnel name, the tunnel can not be established.
If the NAS is pre-provisioned with a default AFTR tunnel name and the
AFTR tunnel name received in Access-Accept is different from the
configured default, then the AFTR tunnel name received in the Access-
Accept message MUST be used for the session.
If the NAS cannot support the received AFTR tunnel name for any
reason, the tunnel should not be established.
When the Access-Request is triggered by a DHCPv6 Rebind message if
the AFTR tunnel name received in the Access-Accept is different from
the currently used one for that session, the NAS MUST force the B4 to
re-establish the tunnel using the new AFTR name received in the
Access-Accept message.
If an implementation includes the Change-of-Authorization (CoA)
messages [RFC5176], they could be used to modify the current
established DS-Lite tunnel. When the NAS receives a CoA Request
message containing the DS-Lite-Tunnel-Name attribute, the NAS MUST
send a Reconfigure message to a B4 to inform the B4 that the NAS has
new or updated configuration parameters and that the B4 is to
initiate a Renew/Reply or Information-request/Reply transaction with
the NAS in order to receive the updated information.
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Upon receiving an AFTR tunnel name different from the currently used
one, the B4 MUST terminate the current DS-Lite tunnel and the B4 MUST
establish a new DS-LITE tunnel with the specified AFTR.
The DS-Lite-Tunnel-Name RADIUS attribute MAY be present in
Accounting-Request records where the Acct-Status-Type is set to
Start, Stop or Interim-Update. The DS-Lite-Tunnel-Name RADIUS
attribute MUST NOT appear more than once in a message.
A summary of the DS-Lite-Tunnel-Name RADIUS attribute format is shown
below. The fields are transmitted from left to right.
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 | DS-Lite-Tunnel-Name(FQDN)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
TBA1 for DS-Lite-Tunnel-Name.
Length:
This field indicates the total length in octets of this
attribute including the Type, the Length fields and the length
in octets of the DS-Lite-Tunnel-Name field
DS-Lite-Tunnel-Name:
A single Fully Qualified Domain Name of the remote tunnel
endpoint, located at the DS-Lite AFTR.
As the DS-Lite-Tunnel-Name attribute is used to populate the DHCPv6
OPTION_AFTR_NAME option, the DS-Lite-Tunnel-Name field is formatted
as required in DHCPv6 (Section 8 of [RFC3315] "Representation and Use
of Domain Names"). Briefly, the format described is using a single
octet noting the length of one DNS label (limited to at most 63
octets), followed by the label contents. This repeats until all
labels in the FQDN are exhausted, including a terminating zero-length
label. Any updates to Section 8 of [RFC3315] also apply to encoding
of this field.
5. Table of attributes
The following tables provide a guide to which attributes may be found
in which kinds of packets, and in what quantity.
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Access- Access- Access- Challenge Accounting # Attribute
Request Accept Reject Request
0-1 0-1 0 0 0-1 TBA1 DS-Lite-Tunnel-Name
CoA-Request CoA-ACK CoA-NACK # Attribute
0-1 0 0 TBA1 DS-Lite-Tunnel-Name
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.
6. Security Considerations
This document has no additional security considerations beyond those
already identified in [RFC2865]
[RFC6333] discusses Dual-Stack Lite related security issues.
7. IANA Considerations
This document requests the allocation of a new Radius attribute types
from the IANA registry "Radius Attribute Types" located at
http://www.iana.org/assignments/radius-types
DS-Lite-Tunnel-Name - TBA1
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
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Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, August 2011.
8.2. Informative References
[I-D.ietf-radext-ipv6-access]
Lourdelet, B., Dec, W., Sarikaya, B., Zorn, G., and D.
Miles, "RADIUS attributes for IPv6 Access Networks",
draft-ietf-radext-ipv6-access-05 (work in progress),
July 2011.
[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,
January 2008.
Authors' Addresses
Roberta Maglione
Telecom Italia
Via Reiss Romoli 274
Torino 10148
Italy
Phone:
Email: roberta.maglione@telecomitalia.it
Alain Durand
Juniper Networks
1194 North Mathilda Avenue
Sunnyvale, CA 94089-1206
USA
Phone:
Fax:
Email: adurand@juniper.net
URI:
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