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Versions: (draft-guo-softwire-6rd-radius-attrib) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 6930

Network Working Group                                       Dayong Guo
Internet Draft                                    Sheng Jiang (Editor)
Intended status: Standards Track          Huawei Technologies Co., Ltd
Expires: July 28, 2013                                      R. Despres
                                                             RD-IPtech
                                                           R. Maglione
                                                        Telecom Italia
                                                      January 24, 2013



                        RADIUS Attribute for 6rd

              draft-ietf-softwire-6rd-radius-attrib-11.txt


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on July 28, 2013.

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   Copyright (c) 2013 IETF Trust and the persons identified as the
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Abstract

   IPv6 Rapid Deployment (6rd) provides both IPv4 and IPv6 connectivity
   services simultaneously during the IPv4/IPv6 co-existence period. The
   Dynamic Host Configuration Protocol (DHCP) 6rd option has been
   defined to configure the 6rd Customer Edge (CE). However, in many
   networks, the configuration information may be stored in
   Authentication Authorization and Accounting (AAA) servers while user
   configuration is mainly acquired from a Broadband Network Gateway
   (BNG) through the DHCP protocol. This document defines a Remote
   Authentication Dial In User Service (RADIUS) attribute that carries
   6rd configuration information from the AAA server to BNGs.



Table of Contents

   1. Introduction ................................................ 3
   2. Terminology ................................................. 3
   3. IPv6 6rd Configuration with RADIUS .......................... 3
   4. Attributes .................................................. 6
      4.1. IPv6-6rd-Configuration Attribute ....................... 6
      4.2. Table of attributes .................................... 8
   5. Diameter Considerations ..................................... 9
   6. Security Considerations ..................................... 9
   7. IANA Considerations ........................................ 10
   8. Acknowledgments ............................................ 10
   9. References ................................................. 10
      9.1. Normative References .................................. 10
      9.2. Informative References ................................ 11
















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1. Introduction

   Recently providers have started to deploy IPv6 and to consider
   transition to IPv6. IPv6 Rapid Deployment (6rd) [RFC5969] provides
   both IPv4 and IPv6 connectivity services simultaneously during the
   IPv4/IPv6 co-existence period. 6rd is used to provide IPv6
   connectivity service through legacy IPv4-only infrastructure. 6rd
   uses Dynamic Host Configuration Protocol (DHCP) [RFC2131] and the 6rd
   Customer Edge (CE) uses the DHCP 6rd option [RFC5969] to discover a
   6rd border relay and to configure IPv6 prefix and address.

   In many networks, user configuration information is managed by AAA
   (Authentication, Authorization, and Accounting) servers. The Remote
   Authentication Dial-In User Service (RADIUS) protocol [RFC2865] is
   usually used by AAA servers to communicate with network elements. In
   a fixed line broadband network, the Broadband Network Gateways (BNGs)
   act as the access gateway for users. The BNGs are assumed to embed a
   DHCP server function that allows them to handle locally any DHCP
   requests issued by hosts.

   Since the 6rd configuration information is stored in AAA servers and
   user configuration is mainly through DHCP between BNGs and hosts/CEs,
   new RADIUS attributes are needed to propagate the information from
   AAA servers to BNGs.

2. Terminology

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

   The terms 6rd Customer Edge (6rd CE) and 6rd Border Relay (BR) are
   defined in [RFC5969].

3. IPv6 6rd Configuration with RADIUS

   Figure 1 illustrates how the RADIUS protocol and DHCP cooperate to
   provide 6rd CE with 6rd configuration information.









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      6rd CE                       BNG                       AAA Server
         |                          |                             |
         |-------DHCPDISCOVER------>|                             |
         |(Parameter Request w/ 6rd option)                       |
         |                          |--Access-Request(6rd Attr)-->|
         |                          |                             |
         |                          |<--Access-Accept(6rd Attr)---|
         |<-------DHCPOFFER---------|                             |
         |      (6rd option)        |                             |
         |                          |                             |
                   DHCP                         RADIUS
             Figure 1: the cooperation between DHCP and RADIUS
                       combining with RADIUS authentication

   The BNG acts as a client of RADIUS and as a DHCP server. First, the
   6rd CE MAY initiate a DHCPDISCOVER message that includes a Parameter
   Request option (55) [RFC2132] with the 6rd option [RFC5969]. When the
   BNG receives the DHCPDISCOVER, it SHOULD initiate a RADIUS Access-
   Request message, in which the User-Name attribute (1) SHOULD be
   filled by the 6rd CE MAC address, to the RADIUS server and the User-
   password (2) attribute SHOULD be filled by the shared 6rd password
   that has been preconfigured on the DHCP server, requesting
   authentication as defined in [RFC2865] with IPv6-6rd-Configuration
   attribute, defined in the next Section, in the desired attribute
   list. If the authentication request is approved by the AAA server, an
   Access-Accept message MUST be acknowledged with the IPv6-6rd-
   Configuration Attribute. Then, the BNG SHOULD respond to the 6rd CE
   with a DHCPOFFER message, which contains a DHCP 6rd option. The
   recommended format of the MAC address is as defined in Calling-
   Station-Id ([RFC3580] Section 3.20) without the SSID (Service Set
   Identifier) portion.

   Figure 2 describes another scenario - later re-authorize - in which
   the authorization operation is not coupled with authentication.
   Authorization relevant to 6rd is done independently after the
   authentication process.












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      6rd CE                       BNG                       AAA Server
         |                          |                             |
         |--------DHCPREQUEST------>|                             |
         |(Parameter Request w/ 6rd option)                       |
         |                          |--Access-Request(6rd Attr)-->|
         |                          |                             |
         |                          |<--Access-Accept(6rd Attr)---|
         |                          |                             |
         |<---------DHCPACK---------|                             |
         |      (6rd option)        |                             |
         |                          |                             |
                   DHCP                         RADIUS
              Figure 2: the cooperation between DHCP and RADIUS
                        decoupled with RADIUS authentication

   In this scenario, the Access-Request packet SHOULD contain a Service-
   Type attribute (6) with the value Authorize Only (17); thus,
   according to [RFC5080], the Access-Request packet MUST contain a
   State attribute that obtains from the previous authentication
   process.



   In both above-mentioned scenarios, Message-authenticator (type 80)
   [RFC2865] SHOULD be used to protect both Access-Request and Access-
   Accept messages.

   After receiving the IPv6-6rd-Configuration Attribute in the initial
   Access-Accept, the BNG SHOULD store the received 6rd configuration
   parameters locally. When the 6rd CE sends a DHCP Request message to
   request an extension of the lifetime for the assigned address, the
   BNG does not have to initiate a new Access-Request towards the AAA
   server to request the 6rd configuration parameters. The BNG could
   retrieve the previously stored 6rd configuration parameters and use
   them in its reply.

   If the BNG does not receive the IPv6-6rd-Configuration Attribute in
   the Access-Accept it MAY fall back to a pre-configured default 6rd
   configuration, if any. If the BNG does not have any pre-configured
   default 6rd configuration or if the BNG receives an Access-Reject,
   the tunnel cannot be established.

   As specified in [RFC2131], section 4.4.5, "Reacquisition and
   expiration", if the DHCP server to which the DHCP Request message was
   sent at time T1 has not responded by time T2 (typically
   0.375*duration_of_lease after T1), the 6rd CE (the DHCP client)
   SHOULD enter the REBINDING state and attempt to contact any server.


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   In this situation, the secondary BNG receiving the new DHCP message
   MUST initiate a new Access-Request towards the AAA server. The
   secondary BNG MAY include the IPv6-6rd-Configuration Attribute in its
   Access-Request.

4. Attributes

   This section defines IPv6-6rd-Configuration Attribute which is used
   in the both abovementioned scenarios. The attribute design follows
   [RFC6158] and referring to [I-D.ietf-radext-radius-extensions].

4.1. IPv6-6rd-Configuration Attribute

   The specification requires that multiple IPv4 addresses are
   associated with one IPv6 prefix. Given that RADIUS currently has no
   recommended way of grouping multiple attributes, the design below
   appears to be a reasonable compromise. The IPv6-6rd-Configuration
   Attribute is structured as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |    Length     |    SubType1   |    SubLen1    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          IPv4MaskLen                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    SubType2   |    SubLen2    |  Reserved     |  6rdPrefixLen |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                           6rdPrefix                           +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   SubType3    |    SubLen3    |        6rdBRIPv4Address       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        6rdBRIPv4Address       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type

         TBD

       Length



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         28 + n*6 (the length of the entire attribute in octets; n
         stands for the number of BR IPv4 addresses, minimum n is 1).

       SubType1

         1 (SubType number, for the IPv4 Mask Length suboption)

       SubLen1

         6 (the length of the IPv4 Mask Length suboption)

       IPv4MaskLen

         The number of high-order bits that are identical across all CE
         IPv4 addresses within a given 6rd domain. This may be any value
         between 0 and 32. Any value greater than 32 is invalid. Since
         [RFC6158] Section A.2.1 has forbidden 8-bit fields, a 32-bit
         field is used here.

       SubType2

         2 (SubType number, for the 6rd prefix suboption)

       SubLen2

         20 (the length of the 6rd prefix suboption)

       Reserved

         Set to be all 0 for now. Reserved for future use. To be
         compatible with other IPv6 prefix attributes in the RADIUS
         Protocol. The bits MUST be set to zero by the sender and MUST
         be ignored by the receiver.

       6rdPrefixLen

         The IPv6 Prefix length of the Service Provider's 6rd IPv6
         prefix in number of bits. The 6rdPrefixLen MUST be less than or
         equal to 128.

       6rdPrefix

         The Service Provider's 6rd IPv6 prefix represented as a 16
         octet IPv6 address. The bits after the 6rdPrefixlen number of
         bits in the prefix SHOULD be set to zero.

       SubType3


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         3 (SubType number, for the 6rd Border Relay IPv4 address
         suboption)

       SubLen3

         6 (the length of the 6rd Border Relay IPv4 address suboption)

       6rdBRIPv4Address

         One or more IPv4 addresses of the 6rd Border Relay(s) for a
         given 6rd domain. The maximum RADIUS Attribute length of 255
         octets results in a limit of 37 IPv4 addresses.

   Since the subtypes have values, they can appear in any order. If
   multiple 6rdBRIPv4Address (subtype 3) appear, they are RECOMMENDED to
   be placed together.

   The IPv6-6rd-Configuration Attribute is normally used in the
   Access-Accept messages. It MAY be used in Access-Request packets as a
   hint to the RADIUS server; for example if the BNG is pre-configured
   with a default 6rd configuration, these parameters MAY be inserted in
   the attribute. The RADIUS server MAY ignore the hint sent by the BNG
   and it MAY assign different 6rd parameters.

   If the BNG includes the IPv6-6rd-Configuration Attribute, but the AAA
   server does not recognize it, this attribute MUST be ignored by the
   AAA Server.

   If the BNG does not receive the IPv6-6rd-Configuration Attribute in
   the Access-Accept it MAY fallback to a pre-configured default 6rd
   configuration, if any. If the BNG does not have any pre-configured
   default 6rd configuration, the 6rd tunnel cannot be established.

   If the BNG is pre-provisioned with a default 6rd configuration and
   the 6rd configuration received in Access-Accept is different from the
   configured default, then the 6rd configuration received in the
   Access-Accept message MUST be used for the session.

   If the BNG cannot support the received 6rd configuration for any
   reason, the tunnel SHOULD NOT be established.

4.2. Table of attributes

   The following table adds to the one in [RFC2865], Section 5.44,
   providing a guide to the quantity of IPv6-6rd-Configuration
   attributes that may be found in each kind of packet.



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   Request Accept Reject Challenge Accounting  #  Attribute
                                    Request
    0-1     0-1     0      0         0-1      TBD  IPv6-6rd-
                                                   Configuration
    0-1     0-1     0      0         0-1      1    User-Name
    0-1     0       0      0         0-1      2    User-Password
    0-1     0-1     0      0         0-1      6    Service-Type
    0-1     0-1     0-1    0-1       0-1      80   Message-Authenticator

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

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

5. Diameter Considerations

   This attribute is usable within either RADIUS or Diameter [RFC6733].
   Since the Attributes defined in this document will be allocated from
   the standard RADIUS type space, no special handling is required by
   Diameter entities.

6. Security Considerations

   In 6rd scenarios, both CE and BNG are within a provider network,
   which can be considered as a closed network and a lower security
   threat environment. A similar consideration can be applied to the
   RADIUS message exchange between BNG and the AAA server.

   In 6rd scenarios, the RADIUS protocol is run over IPv4. Known
   security vulnerabilities of the RADIUS protocol are discussed in
   [RFC2607], [RFC2865], and [RFC2869]. Use of IPsec [RFC4301] for
   providing security when RADIUS is carried in IPv6 is discussed in
   [RFC3162].

   A malicious user may use MAC address proofing and/or dictionary
   attack on the shared 6rd password that has been preconfigured on the
   DHCP server to get unauthorized 6rd configuration information. The
   follow-up secure issues have been considered in Section 12,
   [RFC5969].





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   Security considerations for 6rd specific between 6rd CE and BNG are
   discussed in [RFC5969]. Furthermore, generic DHCP security mechanisms
   can be applied DHCP intercommunication between 6rd CE and BNG.

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

7. IANA Considerations

   This document requests the assignment of one new RADIUS Attribute
   Types in the "RADIUS Types" registry (currently located at
   http://www.iana.org/assignments/radius-types for the following
   attributes:

      o  IPv6-6rd-Configuration

   IANA should allocate the number from the standard RADIUS Attributes
   range (values 1-191).  The RFC Editor should use the assigned value
   to replace "TBD" in Sections 4.1 and 4.2, and should remove this
   paragraph.

8. Acknowledgments

   The authors would like to thank Alan DeKok, Yong Cui, Leaf Yeh, Sean
   Turner, Joseph Salowey, Glen Zorn, Dave Nelson, Bernard Aboba, Benoit
   Claise, Barry Lieba, Stephen Farrell, Adrian Farrel, Ralph Droms and
   other members of Softwire WG, RADIUSExt WG, AAA-Doctors and Secdir
   for valuable comments.

9. References

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2131] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
             March 1997.

   [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
             Extensions", RFC 2132, 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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   [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", RFC
             3162, August 2001.

   [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
             Internet Protocol", RFC 4301, December 2005.

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

   [RFC5969] Townsley, M. and O. Troan, "IPv6 Rapid Deployment on IPv4
             Infrastructures (6rd) -- Protocol Specification", RFC5969,
             August 2010.

   [RFC6158] DeKok, A. and G. Weber, "RADIUS Design Guidelines", RFC
             6158, March 2011.

   [RFC6733] V. Fajardo, Ed., J. Arkko, J. Loughney, G. Zorn, Ed.,
             "Diameter Base Protocol", RFC 6733, October 2012.

9.2. Informative References

   [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
             Implementation in Roaming", RFC 2607, June 1999.

   [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
             Extensions", RFC 2869, June 2000.

   [RFC3580] Congdon, P., B. Aboba, A. Smith, G. Zorn and J. Roese,
             "IEEE 802.1X Remote Authentication Dial In User Service
             (RADIUS) Usage Guidelines", RFC 3580, September 2003.

   [I-D.ietf-radext-radius-extensions]
             DeKok, A. and A. Lior, "Remote Authentication Dial In User
             Service (RADIUS) Protocol Extensions", draft-ietf-radext-
             radius-extensions, work in process.












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   Author's Addresses

   Dayong Guo
   Huawei Technologies Co., Ltd
   Q14 Huawei Campus, 156 BeiQi Road,
   ZhongGuan Cun, Hai-Dian District, Beijing 100095
   P.R. China
   Email: guoseu@huawei.com

   Sheng Jiang (Editor)
   Huawei Technologies Co., Ltd
   Q14 Huawei Campus, 156 BeiQi Road,
   ZhongGuan Cun, Hai-Dian District, Beijing 100095
   P.R. China
   Email: jiangsheng@huawei.com

   Remi Despres
   RD-IPtech
   3 rue du President Wilson
   Levallois,
   France
   Email: despres.remi@laposte.net

   Roberta Maglione
   Telecom Italia
   Via Reiss Romoli 274
   Torino 10148
   Italy
   Email: roberta.maglione@telecomitalia.it



















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