RADIUS and IPv6
RFC 3162

Network Working Group                                           B. Aboba
Request for Comments: 3162                                     Microsoft
Category: Standards Track                                        G. Zorn
                                                           Cisco Systems
                                                               D. Mitton
                                                   Circular Logic UnLtd.
                                                             August 2001

                            RADIUS and IPv6

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document specifies the operation of RADIUS (Remote
   Authentication Dial In User Service) when run over IPv6 as well as
   the RADIUS attributes used to support IPv6 network access.

1.  Introduction

   This document specifies the operation of RADIUS [4]-[8] over IPv6
   [13] as well as the RADIUS attributes used to support IPv6 network
   access.

   Note that a NAS sending a RADIUS Access-Request may not know a-priori
   whether the host will be using IPv4, IPv6, or both.  For example,
   within PPP, IPv6CP [11] occurs after LCP, so that address assignment
   will not occur until after RADIUS authentication and authorization
   has completed.

   Therefore it is presumed that the IPv6 attributes described in this
   document MAY be sent along with IPv4-related attributes within the
   same RADIUS message and that the NAS will decide which attributes to
   use.  The NAS SHOULD only allocate addresses and prefixes that the
   client can actually use, however.  For example, there is no need for

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RFC 3162                    RADIUS and IPv6                  August 2001

   the NAS to reserve use of an IPv4 address for a host that only
   supports IPv6; similarly, a host only using IPv4 or 6to4 [12] does
   not require allocation of an IPv6 prefix.

   The NAS can provide IPv6 access natively, or alternatively, via other
   methods such as IPv6 within IPv4 tunnels [15] or 6over4 [14].  The
   choice of method for providing IPv6 access has no effect on RADIUS
   usage per se, although if it is desired that an IPv6 within IPv4
   tunnel be opened to a particular location, then tunnel attributes
   should be utilized, as described in [6], [7].

1.1.  Requirements language

   In this document, the key words "MAY", "MUST, "MUST NOT", "optional",
   "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as
   described in [1].

2.  Attributes

2.1.  NAS-IPv6-Address

   Description

      This Attribute indicates the identifying IPv6 Address of the NAS
      which is requesting authentication of the user, and SHOULD be
      unique to the NAS within the scope of the RADIUS server.  NAS-
      IPv6-Address is only used in Access-Request packets.  NAS-IPv6-
      Address and/or NAS-IP-Address MAY be present in an Access-Request
      packet; however, if neither attribute is present then NAS-
      Identifier MUST be present.

   A summary of the NAS-IPv6-Address 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     |             Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Address             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Type

      95 for NAS-IPv6-Address

   Length

      18

   Address

      The Address field is 16 octets.

3.2.  Framed-Interface-Id

   Description

      This Attribute indicates the IPv6 interface identifier to be
      configured for the user.  It MAY be used in Access-Accept packets.
      If the Interface-Identifier IPv6CP option [11] has been
      successfully negotiated, this Attribute MUST be included in an
      Access-Request packet as a hint by the NAS to the server that it
      would prefer that value.  It is recommended, but not required,
      that the server honor the hint.

   A summary of the Framed-Interface-Id 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     |             Interface-Id
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Interface-Id
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Interface-Id             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      96 for Framed-Interface-Id

   Length

      10

   Interface-Id

      The Interface-Id field is 8 octets.

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2.3.  Framed-IPv6-Prefix

   Description

      This Attribute indicates an IPv6 prefix (and corresponding route)
      to be configured for the user.  It MAY be used in Access-Accept
      packets, and can appear multiple times.  It MAY be used in an
      Access-Request packet as a hint by the NAS to the server that it
      would prefer these prefix(es), but the server is not required to
      honor the hint.  Since it is assumed that the NAS will plumb a
      route corresponding to the prefix, it is not necessary for the
      server to also send a Framed-IPv6-Route attribute for the same
      prefix.

   A summary of the Framed-IPv6-Prefix 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     |  Reserved     | Prefix-Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Prefix
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Prefix
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Prefix
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Prefix                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      97 for Framed-IPv6-Prefix

   Length

      At least 4 and no larger than 20.

   Reserved

      This field, which is reserved and MUST be present, is always set
      to zero.

   Prefix-Length

      The length of the prefix, in bits.  At least 0 and no larger than
      128.

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   Prefix

      The Prefix field is up to 16 octets in length.  Bits outside of
      the Prefix-Length, if included, must be zero.

2.4.  Login-IPv6-Host

   Description

      This Attribute indicates the system with which to connect the
      user, when the Login-Service Attribute is included.  It MAY be
      used in Access-Accept packets.  It MAY be used in an Access-
      Request packet as a hint to the server that the NAS would prefer
      to use that host, but the server is not required to honor the
      hint.

   A summary of the Login-IPv6-Host 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     |             Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      98 for Login-IPv6-Host

   Length

      18

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   Address

      The Address field is 16 octets in length.  The value
      0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF indicates that the NAS SHOULD
      allow the user to select an address or name to be connected to.
      The value 0 indicates that the NAS SHOULD select a host to connect
      the user to.  Other values indicate the address the NAS SHOULD
      connect the user to.

2.5.  Framed-IPv6-Route

   Description

      This Attribute provides routing information to be configured for
      the user on the NAS.  It is used in the Access-Accept packet and
      can appear multiple times.

   A summary of the Framed-IPv6-Route Attribute format is shown below.
   The fields are transmitted from left to right.

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

   Type

      99 for Framed-IPv6-Route

   Length

      >=3

   Text

      The Text field is one or more octets, and its contents are
      implementation dependent.  The field is not NUL (hex 00)
      terminated.  It is intended to be human readable and MUST NOT
      affect operation of the protocol.

      For IPv6 routes, it SHOULD contain a destination prefix optionally
      followed by a slash and a decimal length specifier stating how
      many high order bits of the prefix to use.  That is followed by a
      space, a gateway address, a space, and one or more metrics
      (encoded in decimal) separated by spaces.  Prefixes and addresses
      are formatted as described in [16].  For example,
      "2000:0:0:106::/64 2000::106:a00:20ff:fe99:a998 1".

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      Whenever the gateway address is the IPv6 unspecified address the
      IP address of the user SHOULD be used as the gateway address.  The
      unspecified address can be expressed in any of the acceptable
      formats described in [16].  For example, "2000:0:0:106::/64 :: 1".

2.6.  Framed-IPv6-Pool

   Description

      This Attribute contains the name of an assigned pool that SHOULD
      be used to assign an IPv6 prefix for the user.  If a NAS does not
      support multiple prefix pools, the NAS MUST ignore this Attribute.

   A summary of the Framed-IPv6-Pool Attribute format is shown below.
   The fields are transmitted from left to right.

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

   Type

      100 for Framed-IPv6-Pool

   Length

      >= 3

   String

      The string field contains the name of an assigned IPv6 prefix pool
      configured on the NAS.  The field is not NUL (hex 00) terminated.

3.  Table of Attributes

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

   Request Accept Reject Challenge Accounting  #  Attribute
                                   Request
   0-1     0      0      0         0-1        95  NAS-IPv6-Address
   0-1     0-1    0      0         0-1        96  Framed-Interface-Id
   0+      0+     0      0         0+         97  Framed-IPv6-Prefix
   0+      0+     0      0         0+         98  Login-IPv6-Host
   0       0+     0      0         0+         99  Framed-IPv6-Route
   0       0-1    0      0         0-1       100  Framed-IPv6-Pool

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4.  References

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

   [2]   Yergeau, F., "UTF-8, a transformation format of Unicode and ISO
         10646", RFC 2044, October 1996.

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

   [4]   Rigney, C., Rubens, A., Simpson, W. and S. Willens,  "Remote
         Authentication Dial In User Service (RADIUS)", RFC 2865, June
         2000.

   [5]   Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

   [6]   Zorn, G., Mitton, D. and B. Aboba, "RADIUS Accounting
         Modifications for Tunnel Protocol Support", RFC 2867, June
         2000.

   [7]   Zorn, G., Leifer, D., Rubens, A., Shriver, J., Holdrege, M.
         and I. Goyret, "RADIUS Attributes for Tunnel Protocol Support",
         RFC 2868, June 2000.

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

   [9]   Kent S. and R. Atkinson, "Security Architecture for the
         Internet Protocol", RFC 2401, November 1998.

   [10]  Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA
         Considerations Section in RFCs", BCP 26, RFC 2434, October
         1998.

   [11]  Haskin, D. and E. Allen, "IP Version 6 over PPP", RFC 2472,
         December 1998.

   [12]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains via
         IPv4 Clouds", RFC 3056, February 2001.

   [13]  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
         Specification", RFC 2460, December 1998.

   [14]  Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
         Domains without Explicit Tunnels", RFC 2529, March 1999.

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   [15]  Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6
         Hosts and Routers", RFC 2893, August 2000.

   [16]  Hinden, R. and S. Deering, "IP Version 6 Addressing
         Architecture", RFC 2373, July 1998.

5.  Security Considerations

   This document describes the use of RADIUS for the purposes of
   authentication, authorization and accounting in IPv6-enabled
   networks.  In such networks, the RADIUS protocol may run either over
   IPv4 or over IPv6.  Known security vulnerabilities of the RADIUS
   protocol are described in [3], [4] and [8].

   Since IPSEC [9] is mandatory to implement for IPv6, it is expected
   that running RADIUS implementations supporting IPv6 will typically
   run over IPSEC.  Where RADIUS is run over IPSEC and where
   certificates are used for authentication, it may be desirable to
   avoid management of RADIUS shared secrets, so as to leverage the
   improved scalability of public key infrastructure.

   Within RADIUS, a shared secret is used for hiding of attributes such
   as User-Password [4] and Tunnel-Password [7].  In addition, the
   shared secret is used in computation of the Response Authenticator
   [4], as well as the Message-Authenticator attribute [8].  Therefore,
   in RADIUS a shared secret is used to provide confidentiality as well
   as integrity protection and authentication.  As a result, only use of
   IPSEC ESP with a non-null transform can provide security services
   sufficient to substitute for RADIUS application-layer security.
   Therefore, where IPSEC AH or ESP null is used, it will typically
   still be necessary to configure a RADIUS shared secret.

   However, where RADIUS is run over IPSEC ESP with a non-null
   transform, the secret shared between the NAS and the RADIUS server
   MAY NOT be configured.  In this case, a shared secret of zero length
   MUST be assumed.

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6.  IANA Considerations

   This document requires the assignment of six new RADIUS attribute
   numbers for the following attributes:

      NAS-IPv6-Address
      Framed-Interface-Id
      Framed-IPv6-Prefix
      Login-IPv6-Host
      Framed-IPv6-Route
      Framed-IPv6-Pool

   See section 3 for the registered list of numbers.

7.  Acknowledgments

   The authors would like to acknowledge Jun-ichiro itojun Hagino of IIJ
   Research Laboratory, Darran Potter of Cisco and Carl Rigney of Lucent
   for contributions to this document.

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8.  Authors' Addresses

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425 936 6605
   Fax:   +1 425 936 7329
   EMail: bernarda@microsoft.com

   Glen Zorn
   Cisco Systems, Inc.
   500 108th Avenue N.E., Suite 500
   Bellevue, WA 98004

   Phone: +1 425 471 4861
   EMail: gwz@cisco.com

   Dave Mitton
   Circular Logic UnLtd.
   733 Turnpike Street #154
   North Andover, MA 01845

   Phone: 978 683-1814
   Email: david@mitton.com

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Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

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   The limited permissions granted above are perpetual and will not be
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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