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RFC 4675 - RADIUS Attributes for Virtual LAN and Priority Support


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Network Working Group                                         P. Congdon
Request for Comments: 4675                                    M. Sanchez
Category: Standards Track                        Hewlett-Packard Company
                                                                B. Aboba
                                                   Microsoft Corporation
                                                          September 2006

         RADIUS Attributes for Virtual LAN and Priority Support

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 (2006).

Abstract

   This document proposes additional Remote Authentication Dial-In User
   Service (RADIUS) attributes for dynamic Virtual LAN assignment and
   prioritization, for use in provisioning of access to IEEE 802 local
   area networks.  These attributes are usable within either RADIUS or
   Diameter.

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................3
      1.2. Requirements Language ......................................3
      1.3. Attribute Interpretation ...................................3
   2. Attributes ......................................................4
      2.1. Egress-VLANID ..............................................4
      2.2. Ingress-Filters ............................................6
      2.3. Egress-VLAN-Name ...........................................7
      2.4. User-Priority-Table ........................................8
   3. Table of Attributes ............................................10
   4. Diameter Considerations ........................................10
   5. IANA Considerations ............................................11
   6. Security Considerations ........................................11
   7. References .....................................................12
      7.1. Normative References ......................................12
      7.2. Informative References ....................................13
   8. Acknowledgements ...............................................13

1.  Introduction

   This document describes Virtual LAN (VLAN) and re-prioritization
   attributes that may prove useful for provisioning of access to IEEE
   802 local area networks [IEEE-802] with the Remote Authentication
   Dial-In User Service (RADIUS) or Diameter.

   While [RFC3580] enables support for VLAN assignment based on the
   tunnel attributes defined in [RFC2868], it does not provide support
   for a more complete set of VLAN functionality as defined by
   [IEEE-802.1Q].  The attributes defined in this document provide
   support within RADIUS and Diameter analogous to the management
   variables supported in [IEEE-802.1Q] and MIB objects defined in
   [RFC4363].  In addition, this document enables support for a wider
   range of [IEEE-802.1X] configurations.

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.  Also known as a RADIUS client.

   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

   The attributes described in this document apply to a single instance
   of a NAS port, or more specifically an IEEE 802.1Q bridge port.
   [IEEE-802.1Q], [IEEE-802.1D], and [IEEE-802.1X] do not recognize
   finer management granularity than "per port".  In some cases, such as
   with IEEE 802.11 wireless LANs, the concept of a "virtual port" is
   used in place of the physical port.  Such virtual ports are typically
   based on security associations and scoped by station, or Media Access
   Control (MAC) address.

   The attributes defined in this document are applied on a per-user
   basis and it is expected that there is a single user per port;
   however, in some cases that port may be a "virtual port".  If a NAS
   implementation conforming to this document supports "virtual ports",
   it may be possible to provision those "virtual ports" with unique
   values of the attributes described in this document, allowing
   multiple users sharing the same physical port to each have a unique
   set of authorization parameters.

   If a NAS conforming to this specification receives an Access-Accept
   packet containing an attribute defined in this document that 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 the 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 preexisting configuration remains unchanged.  As
   a result, no accounting packets should be generated.

2.  Attributes

2.1.  Egress-VLANID

   Description

      The Egress-VLANID attribute represents an allowed IEEE 802 Egress
      VLANID for this port, indicating if the VLANID is allowed for
      tagged or untagged frames as well as the VLANID.

      As defined in [RFC3580], the VLAN assigned via tunnel attributes
      applies both to the ingress VLANID for untagged packets (known as
      the PVID) and the egress VLANID for untagged packets.  In
      contrast, the Egress-VLANID attribute configures only the egress
      VLANID for either tagged or untagged packets.  The Egress-VLANID
      attribute MAY be included in the same RADIUS packet as [RFC3580]
      tunnel attributes; however, the Egress-VLANID attribute is not
      necessary if it is being used to configure the same untagged
      VLANID included in tunnel attributes.  To configure an untagged
      VLAN for both ingress and egress, the tunnel attributes of
      [RFC3580] MUST be used.

      Multiple Egress-VLANID attributes MAY be included in Access-
      Request, Access-Accept, CoA-Request, or Accounting-Request
      packets; this attribute MUST NOT be sent within an Access-
      Challenge, Access-Reject, Disconnect-Request, Disconnect-ACK,

      Disconnect-NAK, CoA-ACK, or CoA-NAK.  Each attribute adds the
      specified VLAN to the list of allowed egress VLANs for the port.

      The Egress-VLANID attribute 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     |            Value
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      56

   Length

      6

   Value

      The Value field is four octets.  The format is described below:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Tag Indic.   |        Pad            |       VLANID          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Tag Indication field is one octet in length and indicates
      whether the frames on the VLAN are tagged (0x31) or untagged
      (0x32).  The Pad field is 12 bits in length and MUST be 0 (zero).
      The VLANID is 12 bits in length and contains the [IEEE-802.1Q]
      VLAN VID value.

2.2.  Ingress-Filters

   Description

      The Ingress-Filters attribute corresponds to the Ingress Filter
      per-port variable defined in [IEEE-802.1Q] clause 8.4.5.  When the
      attribute has the value "Enabled", the set of VLANs that are
      allowed to ingress a port must match the set of VLANs that are
      allowed to egress a port.  Only a single Ingress-Filters attribute
      MAY be sent within an Access-Request, Access-Accept, CoA-Request,
      or Accounting-Request packet; this attribute MUST NOT be sent
      within an Access-Challenge, Access-Reject, Disconnect-Request,
      Disconnect-ACK, Disconnect-NAK, CoA-ACK, or CoA-NAK.

      The Ingress-Filters attribute 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     |         Value
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      57

   Length

      6

   Value

      The Value field is four octets.  Supported values include:

      1 - Enabled
      2 - Disabled

2.3.  Egress-VLAN-Name

   Description

      Clause 12.10.2.1.3 (a) in [IEEE-802.1Q] describes the
      administratively assigned VLAN Name associated with a VLAN-ID
      defined within an IEEE 802.1Q bridge.  The Egress-VLAN-Name
      attribute represents an allowed VLAN for this port.  It is similar
      to the Egress-VLANID attribute, except that the VLAN-ID itself is
      not specified or known; rather, the VLAN name is used to identify
      the VLAN within the system.

      The tunnel attributes described in [RFC3580] and the Egress-VLAN-
      Name attribute both can be used to configure the egress VLAN for
      untagged packets.  These attributes can be used concurrently and
      MAY appear in the same RADIUS packet.  When they do appear
      concurrently, the list of allowed VLANs is the concatenation of
      the Egress-VLAN-Name and the Tunnel-Private-Group-ID (81)
      attributes.  The Egress-VLAN-Name attribute does not alter the
      ingress VLAN for untagged traffic on a port (also known as the
      PVID).  The tunnel attributes from [RFC3580] should be relied upon
      instead to set the PVID.

      The Egress-VLAN-Name attribute contains two parts; the first part
      indicates if frames on the VLAN for this port are to be
      represented in tagged or untagged format, the second part is the
      VLAN name.

      Multiple Egress-VLAN-Name attributes MAY be included within an
      Access-Request, Access-Accept, CoA-Request, or Accounting-Request
      packet; this attribute MUST NOT be sent within an Access-
      Challenge, Access-Reject, Disconnect-Request, Disconnect-ACK,
      Disconnect-NAK, CoA-ACK, or CoA-NAK.  Each attribute adds the
      named VLAN to the list of allowed egress VLANs for the port.  The
      Egress-VLAN-Name attribute 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 Indic.  |   String...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      58

   Length

      >=4

   Tag Indication

      The Tag Indication field is one octet in length and indicates
      whether the frames on the VLAN are tagged (0x31, ASCII '1') or
      untagged (0x32, ASCII '2').  These values were chosen so as to
      make them easier for users to enter.

   String

      The String field is at least one octet in length and contains the
      VLAN Name as defined in [IEEE-802.1Q] clause 12.10.2.1.3 (a).
      [RFC3629] UTF-8 encoded 10646 characters are RECOMMENDED, but a
      robust implementation SHOULD support the field as undistinguished
      octets.

2.4.  User-Priority-Table

   Description

      [IEEE-802.1D] clause 7.5.1 discusses how to regenerate (or re-map)
      user priority on frames received at a port.  This per-port
      configuration enables a bridge to cause the priority of received
      traffic at a port to be mapped to a particular priority.
      [IEEE-802.1D] clause 6.3.9 describes the use of remapping:

         The ability to signal user priority in IEEE 802 LANs allows
         user priority to be carried with end-to-end significance across
         a Bridged Local Area Network.  This, coupled with a consistent
         approach to the mapping of user priority to traffic classes and
         of user priority to access_priority, allows consistent use of
         priority information, according to the capabilities of the
         Bridges and MACs in the transmission path...

         Under normal circumstances, user priority is not modified in
         transit through the relay function of a Bridge; however,
         network management can control how user priority is propagated.
         Table 7-1 provides the ability to map incoming user priority
         values on a per-Port basis.  By default, the regenerated user
         priority is identical to the incoming user priority.

      This attribute represents the IEEE 802 prioritization that will be
      applied to frames arriving at this port.  There are eight possible
      user priorities, according to the [IEEE-802] standard.
      [IEEE-802.1D] clause 14.6.2.3.3 specifies the regeneration table

      as 8 values, each an integer in the range 0-7.  The management
      variables are described in clause 14.6.2.2.

      A single User-Priority-Table attribute MAY be included in an
      Access-Accept or CoA-Request packet; this attribute MUST NOT be
      sent within an Access-Request, Access-Challenge, Access-Reject,
      Disconnect-Request, Disconnect-ACK, Disconnect-NAK, CoA-ACK, CoA-
      NAK or Accounting-Request.  Since the regeneration table is only
      maintained by a bridge conforming to [IEEE-802.1D], this attribute
      should only be sent to a RADIUS client supporting that
      specification.

      The User-Priority-Table attribute 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       |          String
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                    String
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    String            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      59

   Length

      10

   String

      The String field is 8 octets in length and includes a table that
      maps the incoming priority (if it is set -- the default is 0) into
      one of eight regenerated priorities.  The first octet maps to
      incoming priority 0, the second octet to incoming priority 1, etc.
      The values in each octet represent the regenerated priority of the
      frame.

      It is thus possible to either remap incoming priorities to more
      appropriate values; to honor the incoming priorities; or to
      override any incoming priorities, forcing them to all map to a
      single chosen priority.

      The [IEEE-802.1D] specification, Annex G, provides a useful
      description of traffic type - traffic class mappings.

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+   56   Egress-VLANID
    0-1     0-1     0       0        0-1   0-1  57   Ingress-Filters
    0+      0+      0       0        0+    0+   58   Egress-VLAN-Name
    0       0-1     0       0        0-1   0    59   User-Priority-Table

   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

   When used in Diameter, the attributes defined in this specification
   can be used as Diameter attribute-value pair (AVPs) from the Code
   space 1-255 (RADIUS attribute compatibility space).  No additional
   Diameter Code values are therefore allocated.  The data types and
   flag rules for the attributes are as follows:

                                  +---------------------+
                                  |    AVP Flag rules   |
                                  |----+-----+----+-----|----+
                                  |    |     |SHLD| MUST|    |
   Attribute Name      Value Type |MUST| MAY | NOT|  NOT|Encr|
   -------------------------------|----+-----+----+-----|----|
   Egress-VLANID       OctetString| M  |  P  |    |  V  | Y  |
   Ingress-Filters     Enumerated | M  |  P  |    |  V  | Y  |
   Egress-VLAN-Name    UTF8String | M  |  P  |    |  V  | Y  |
   User-Priority-Table OctetString| M  |  P  |    |  V  | Y  |
   -------------------------------|----+-----+----+-----|----|

   The attributes in this specification have no special translation
   requirements for Diameter to RADIUS or RADIUS to Diameter gateways;
   they are copied as is, except for changes relating to headers,
   alignment, and padding.  See also [RFC3588] Section 4.1 and [RFC4005]
   Section 9.

   What this specification says about the applicability of the
   attributes for RADIUS Access-Request packets applies in Diameter to
   AA-Request [RFC4005] or Diameter-EAP-Request [RFC4072].  What is said
   about Access-Challenge applies in Diameter to AA-Answer [RFC4005] or
   Diameter-EAP-Answer [RFC4072] with Result-Code AVP set to
   DIAMETER_MULTI_ROUND_AUTH.

   What is said about Access-Accept applies in Diameter to AA-Answer or
   Diameter-EAP-Answer messages that indicate success.  Similarly, what
   is said about RADIUS Access-Reject packets applies in Diameter to
   AA-Answer or Diameter-EAP-Answer messages that indicate failure.

   What is said about COA-Request applies in Diameter to Re-Auth-Request
   [RFC4005].

   What is said about Accounting-Request applies to Diameter
   Accounting-Request [RFC4005] as well.

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 four
   updates for the section "RADIUS Attribute Types" has been made by the
   IANA.  The RADIUS attributes are:

   56 - Egress-VLANID
   57 - Ingress-Filters
   58 - Egress-VLAN-Name
   59 - User-Priority-Table

6.  Security Considerations

   This specification describes the use of RADIUS and Diameter for
   purposes of authentication, authorization, and accounting in IEEE 802
   local area networks.  RADIUS threats and security issues for this
   application are described in [RFC3579] and [RFC3580]; security issues
   encountered in roaming are described in [RFC2607].  For Diameter, the
   security issues relating to this application are described in
   [RFC4005] and [RFC4072].

   This document specifies new attributes that can be included in
   existing RADIUS packets, which are protected as described in
   [RFC3579] and [RFC3576].  In Diameter, the attributes are protected
   as specified in [RFC3588].  See those documents for a more detailed
   description.

   The security mechanisms supported in RADIUS and Diameter are focused
   on preventing an attacker from spoofing packets or modifying packets
   in transit.  They do not prevent an authorized RADIUS/Diameter server
   or proxy from inserting attributes with malicious intent.

   VLAN attributes sent by a RADIUS/Diameter server or proxy may enable
   access to unauthorized VLANs.  These vulnerabilities can be limited
   by performing authorization checks at the NAS.  For example, a NAS
   can be configured to accept only certain VLANIDs from a given
   RADIUS/Diameter server/proxy.

   Similarly, an attacker gaining control of a RADIUS/Diameter server or
   proxy can modify the user priority table, causing either degradation
   of quality of service (by downgrading user priority of frames
   arriving at a port), or denial of service (by raising the level of
   priority of traffic at multiple ports of a device, oversubscribing
   the switch or link capabilities).

7.  References

7.1.  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.

   [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 format of ISO
                 10646", STD 63, RFC 3629, November 2003.

   [RFC4363]     Levi, D. and D. Harrington, "Definitions of Managed
                 Objects for Bridges with Traffic Classes, Multicast
                 Filtering, and Virtual LAN Extensions", RFC 4363,
                 January 2006.

   [IEEE-802]    IEEE Standards for Local and Metropolitan Area
                 Networks:  Overview and Architecture, ANSI/IEEE Std
                 802, 1990.

   [IEEE-802.1D] IEEE Standards for Local and Metropolitan Area
                 Networks: Media Access Control (MAC) Bridges, IEEE Std
                 802.1D-2004, June 2004.

   [IEEE-802.1Q] IEEE Standards for Local and Metropolitan Area
                 Networks: Draft Standard for Virtual Bridged Local Area
                 Networks, P802.1Q-2003, January 2003.

7.2.  Informative References

   [IEEE-802.1X] IEEE Standards for Local and Metropolitan Area
                 Networks: Port based Network Access Control, IEEE Std
                 802.1X-2004, December 2004.

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

   [RFC2868]     Zorn, G., Leifer, D., Rubens, A., Shriver, J.,
                 Holdrege, M., and I. Goyret, "RADIUS Attributes for
                 Tunnel Protocol Support", RFC 2868, June 2000.

   [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 (Remote
                 Authentication Dial In User Service) Support For
                 Extensible Authentication Protocol (EAP)", RFC 3579,
                 September 2003.

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

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

   [RFC4072]     Eronen, P., Hiller, T., and G. Zorn, "Diameter
                 Extensible Authentication Protocol (EAP) Application",
                 RFC 4072, August 2005.

8.  Acknowledgements

   The authors would like to acknowledge Joseph Salowey of Cisco, David
   Nelson of Enterasys, Chuck Black of Hewlett-Packard, and Ashwin
   Palekar of Microsoft.

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
   EMail: paul.congdon@hp.com

   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
   EMail: mauricio.sanchez@hp.com

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

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

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