Network Working Group                                       Paul Congdon
INTERNET-DRAFT                                          Mauricio Sanchez
Category: Proposed Standard                      Hewlett-Packard Company
<draft-ietf-radext-filter-02.txt>                          Bernard Aboba
1 October 2006                                     Microsoft Corporation

                      RADIUS Filter Rule Attribute

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Copyright Notice

   Copyright (C) The Internet Society 2006.


   This document defines the NAS-Filter-Rule attribute within the Remote
   Authentication Dial In User Service (RADIUS), equivalent to the
   Diameter NAS-Filter-Rule AVP described in RFC 4005.

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Table of Contents

1.     Introduction ..........................................    3
   1.1       Terminology .....................................    3
   1.2       Requirements Language ...........................    3
   1.3       Attribute Interpretation ........................    3
2.     NAS-Filter-Rule Attribute .............................    4
3.     Table of Attributes ...................................    5
4.     Diameter Considerations ...............................    5
5.     IANA Considerations ...................................    6
6.     Security Considerations ...............................    6
7.     References ............................................    7
   7.1       Normative References ............................    7
   7.2       Informative References ..........................    7
ACKNOWLEDGMENTS ..............................................    7
AUTHORS' ADDRESSES ...........................................    8
Intellectual Property Statement...............................    9
Disclaimer of Validity........................................    9
Full Copyright Statement .....................................    9

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1.  Introduction

   This document defines the NAS-Filter-Rule attribute within the Remote
   Authentication Dialin User Service (RADIUS) which has the same
   functionality as the Diameter NAS-Filter-Rule AVP (400) defined in
   [RFC4005] Section 6.6.  This attribute may prove useful for
   provisioning of filter rules.

   While [RFC2865] Section 5.11 defines the Filter-Id attribute (11),
   this requires that the NAS be pre-populated with the desired filters.
   However, in situations where the server operator does not know which
   filters have been pre-populated, it useful to specify filter rules

1.1.  Terminology

   This document uses the following terms:

Network Access Server (NAS)
     A device that provides an access service for a user to a network.

RADIUS server
     A RADIUS authentication server is an entity that provides an
     authentication service to a NAS.

RADIUS proxy
     A RADIUS proxy acts as an authentication server to the NAS, and a
     RADIUS client to the RADIUS server.

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

1.3.  Attribute Interpretation

   If a NAS conforming to this specification receives an Access-Accept
   packet containing a NAS-Filter-Rule attribute which it cannot apply,
   it MUST act as though it had received an Access-Reject.  [RFC3576]
   requires that a NAS receiving a  Change of Authorization Request
   (CoA-Request) reply with a CoA-NAK if the Request contains an
   unsupported attribute.  It is recommended that an Error-Cause
   attribute with value set to "Unsupported Attribute" (401) be included
   in the CoA-NAK.  As noted in [RFC3576], authorization changes are
   atomic so that this situation does not result in session termination
   and the pre-existing configuration remains unchanged.  As a result,
   no accounting packets should be generated.

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2.  NAS-Filter-Rule Attribute


      This attribute indicates filter rules to be applied for this user.
      Zero or more NAS-Filter-Rule attributes MAY be sent in Access-
      Accept, CoA-Request, or Accounting-Request packets.

      The NAS-Filter-Rule attribute is not intended to be used
      concurrently with any other filter rule attribute, including
      Filter-Id (11) and NAS-Traffic-Rule [Traffic] attributes, and
      SHOULD NOT appear in the same RADIUS packet.  If a Filter-Id
      attribute is present, then implementations of this specification
      MUST silently discard NAS-Filter-Rule attributes, if present.

      Where more than one NAS-Filter-Rule attribute with the same non-
      zero Tag field value is included in a RADIUS packet, the String
      field of the attributes are to be concatenated to form a single
      filter.  As noted in [RFC2865] Section 2.3, "the forwarding server
      MUST NOT change the order of any attributes of the same type", so
      that RADIUS proxies will not reorder NAS-Filter-Rule attributes.

      A summary of the NAS-Filter-Rule 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     |     Tag       |   String...






      The Tag field is used to identify the filter rule that is
      represented; the length of the Tag field is one octet and it MUST
      always be present.  The Tag field value MUST be in the range
      0x01-0x3F; NAS-Filter-Rule attributes with a Tag field value of
      0x00 are ignored upon receipt.

      Where a single filter rule is less than or equal to 252 octets in

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      length, it MUST be encoded with a tag value of '0' (0x30) and MUST
      NOT be split between multiple NAS-Filter-Rule attributes.  Where a
      single filter rule is split into multiple NAS-Filter-Rule
      attributes, the attributes SHOULD be sent consecutively, without
      intervening attributes with another Tag field value.  On receipt,
      attributes with a Tag value of '0' (0x30) MUST NOT be concatenated
      to form a single filter rule.

      Where a single filter rule exceeds 252 octets in length, the rule
      MUST be encoded across multiple NAS-Filter-Rule attributes, each
      with the same Tag value which MUST NOT be '0' (0x30).  Tag values
      MUST be unique for each filter rule present in a RADIUS packet
      with the exception of a Tag value of '0' (0x30), which may be used
      in multiple attributes, each describing a single filter rule.


      The String field is one or more octets.  It contains filter rules
      in the IPFilterRule syntax defined in [RFC3588] Section 4.3.  A
      robust implementation SHOULD support the field as undistinguished

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.

   Access- Access- Access- Access-   CoA-  Acct-
   Request Accept  Reject  Challenge Req   Req   #   Attribute
    0       0+      0       0        0+    0+   TBD  NAS-Filter-Rule

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

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

4.  Diameter Considerations

   [RFC4005] Section 6.6 defines the NAS-Filter-Rule AVP (400) with the
   same functionality as the RADIUS NAS-Filter-Rule attribute.  In order
   to support interoperability, Diameter/RADIUS gateways will need to be
   configured to translate RADIUS attribute TBD to Diameter AVP 400 and
   vice-versa.  Where a Diameter NAS-Filter-Rule AVP contains a filter
   rule larger than 252 octets, Diameter/RADIUS gateways translate the
   AVP to multiple RADIUS NAS-Filter-Rule attributes, each with the same

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   Tag field value not equal to '0' (0x30).  Similarly, when multiple
   RADIUS NAS-Filter-Rule attributes are received with the same Tag
   field value not equal to '0' (0x30), the String fields of the
   attributes are concatenated together and encoded as the value in a
   single Diameter NAS-Filter-Rule AVP.  RADIUS NAS-Filter-Rule
   attributes with a Tag field of '0' (0x30) are encoded as distinct
   Diameter NAS-Filter-Rule AVPs.

   Note that a translated Diameter message can be larger than the
   maximum RADIUS packet size (4096).  Where a Diameter/RADIUS gateway
   receives a Diameter message containing a NAS-Filter-Rule AVP that is
   too large to fit into a RADIUS packet, the Diameter/RADIUS gateway
   will respond to the originating Diameter peer with the
   DIAMETER_INVALID_AVP_LENGTH error (5014), and with a Failed-AVP AVP
   containing the NAS-Filter-Rule AVP.  Since repairing the error will
   probably require re-working the filter rules, the originating peer
   should treat the combination of a DIAMETER_INVALID_AVP_LENGTH error
   and a Failed-AVP AVP containing a NAS-Filter-Rule AVP as a terminal

5.  IANA Considerations

   This specification does not create any new registries.

   This document uses the RADIUS [RFC2865] namespace, see
   <>.  Allocation of one
   update for the section "RADIUS Attribute Types" is requested. The
   RADIUS attribute for which a value is requested is:

   TBD - NAS-Filter-Rule

6.  Security Considerations

   This specification describes the use of RADIUS for purposes of
   authentication, authorization and accounting.  Threats and security
   issues for this application are described in [RFC3579] and [RFC3580];
   security issues encountered in roaming are described in [RFC2607].

   This document specifies a new attribute that can be included in
   existing RADIUS packets, which are protected as described in
   [RFC3579] and [RFC3576].  See those documents for a more detailed

   A NAS-Filter-Rule attribute sent by a RADIUS server may not be
   understood by the NAS which receives it.  A legacy NAS not compliant
   with this specification may silently discard the NAS-Filter-Rule
   attribute while permitting the user to access the network.  This can
   lead to users improperly receiving unfiltered access to the network.

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   As a result, the NAS-Filter-Rule attribute SHOULD only be sent to a
   NAS that is known to support it.

7.  References

7.1.  Normative references

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

[RFC2865] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote
          Authentication Dial In User Service (RADIUS)", RFC 2865, June

[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
          Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

[RFC3629] Yergeau, F., "UTF-8, a transformation of ISO 10646", RFC 3629,
          November 2003.

[RFC4005] Calhoun, P., Zorn, G., Spence, D. and D. Mitton, "Diameter
          Network Access Server Application", RFC 4005, August 2005.

7.2.  Informative references

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

[RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B.  Aboba,
          "Dynamic Authorization Extensions to Remote Authentication
          Dial In User Service (RADIUS)", RFC 3576, July 2003.

[RFC3579] Aboba, B. and P. Calhoun, "RADIUS Support for Extensible
          Authentication Protocol (EAP)", RFC 3579, September 2003.

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

[Traffic] Congdon, P., Sanchez, M., Lior, A., Adrangi, F. and B. Aboba,
          "Filter Attributes", Internet draft (work in progress), draft-
          ietf-radext-filter-rules-00.txt, February 2006.


   The authors would like to acknowledge Greg Weber of Cisco and David
   Nelson of Enterasys.

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Authors' Addresses

   Paul Congdon
   Hewlett Packard Company
   HP ProCurve Networking
   8000 Foothills Blvd, M/S 5662
   Roseville, CA  95747

   Phone: +1 916 785 5753
   Fax:   +1 916 785 8478

   Mauricio Sanchez
   Hewlett Packard Company
   HP ProCurve Networking
   8000 Foothills Blvd, M/S 5559
   Roseville, CA  95747

   Phone: +1 916 785 1910
   Fax:   +1 916 785 1815

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425 706 6605
   Fax:   +1 425 936 7329

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Open issues

   Open issues relating to this specification are tracked on the
   following web site:

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