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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

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on April 10, 2007.

Copyright Notice

   Copyright (C) The Internet Society 2006.

Abstract

   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
   explicitly.

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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   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

   Description

      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...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      TBD

   Length

      >=4

   Tag

      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.

   String

      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
      octets.

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
   error.

5.  IANA Considerations

   This specification does not create any new registries.

   This document uses the RADIUS [RFC2865] namespace, see
   <http://www.iana.org/assignments/radius-types>.  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
   description.

   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
          2000.

[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.


Acknowledgments

   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

   EMail: paul.congdon@hp.com
   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

   EMail: mauricio.sanchez@hp.com
   Phone: +1 916 785 1910
   Fax:   +1 916 785 1815

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   EMail: bernarda@microsoft.com
   Phone: +1 425 706 6605
   Fax:   +1 425 936 7329





















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Copyright Statement

   Copyright (C) The Internet Society (2006).  This document is subject
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Acknowledgment

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







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Open issues

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

   http://www.drizzle.com/~aboba/RADEXT/













































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