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Versions: (draft-maglione-softwire-dslite-radius-ext) 00 01 02 03 04 05 06 07 RFC 6519

softwire                                                     R. Maglione
Internet-Draft                                            Telecom Italia
Intended status: Standards Track                               A. Durand
Expires: April 19, 2012                                 Juniper Networks
                                                        October 17, 2011


                 RADIUS Extensions for Dual-Stack Lite
                draft-ietf-softwire-dslite-radius-ext-07

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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   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 April 19, 2012.

Copyright Notice




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   Copyright (c) 2011 IETF Trust and the persons identified as the
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   it for publication as an RFC or to translate it into languages other
   than English.



























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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 . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  DS-Lite-Tunnel-Name  . . . . . . . . . . . . . . . . . . .  8
   5.  Table of attributes  . . . . . . . . . . . . . . . . . . . . . 10
   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

   In the scenario depicted in Figure 2 the Access-Request packet
   contains a Service-Type attribute with the value Authorize Only (17),
   thus according to [RFC5080] the Access-Request packet MUST contain a
   State attribute.

   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 IPv4 over
   IPv6 tunnel cannot be established, thus the B4 element has only IPv6
   connectivity.



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4.  RADIUS Attribute

   This section specifies the format of the new RADIUS attribute.

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



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   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.

   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.

   The data type of DS-Lite-Tunnel-Name RADIUS attribute is a string
   with opaque encapsulation, according to section 5 of [RFC2865]




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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.

   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] for RADIUS protocol and in [RFC5176]
   for CoA messages.

   [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.



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   [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.

   [RFC5080]  Nelson, D. and A. DeKok, "Common Remote Authentication
              Dial In User Service (RADIUS) Implementation Issues and
              Suggested Fixes", RFC 5080, December 2007.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              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











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   Alain Durand
   Juniper Networks
   1194 North Mathilda Avenue
   Sunnyvale, CA  94089-1206
   USA

   Phone:
   Fax:
   Email: adurand@juniper.net
   URI:









































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