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Versions: 00 01 02 03 04 05 06 07 RFC 5607

Network Working Group                                          D. Nelson
Internet-Draft                                     Elbrys Networks, Inc.
Intended status: Standards Track                                G. Weber
Expires: May 21, 2008                                  November 18, 2007


 Remote Authentication Dial-In User Service (RADIUS) Authorization for
                 Network Access Server (NAS) Management
           draft-ietf-radext-management-authorization-01.txt

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   This Internet-Draft will expire on May 21, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes Remote Authentication Dial-In User Service
   (RADIUS) attributes for the authorization and service provisioning of
   local and remote management of embedded systems and other managed
   entities, generally referred to as Network Access Servers (NASes).
   Specific provisions are made for remote management via framed
   management protocols, and for granular levels of access rights and
   management privileges.



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Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction and Rationale . . . . . . . . . . . . . . . . . .  3
   3.  Provisions for Framed Management . . . . . . . . . . . . . . .  3
   4.  Provisions for Granular Management Access Rights . . . . . . .  4
   5.  Provisions for Secure Management Access  . . . . . . . . . . .  4
   6.  New Values for Existing RADIUS Attributes  . . . . . . . . . .  4
     6.1.  Service-Type . . . . . . . . . . . . . . . . . . . . . . .  4
   7.  New RADIUS Attributes  . . . . . . . . . . . . . . . . . . . .  5
     7.1.  Framed-Management-Protocol . . . . . . . . . . . . . . . .  6
     7.2.  Management-Transport-Protocol  . . . . . . . . . . . . . .  7
     7.3.  Management-Policy-Id . . . . . . . . . . . . . . . . . . .  8
     7.4.  Management-Privilege-Level . . . . . . . . . . . . . . . . 10
   8.  Examples of attribute groupings  . . . . . . . . . . . . . . . 11
   9.  Diameter Translation Considerations  . . . . . . . . . . . . . 13
   10. RADIUS Proxy Operation Considerations  . . . . . . . . . . . . 13
   11. Table of Attributes  . . . . . . . . . . . . . . . . . . . . . 14
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   13. Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   14. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     15.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
   Intellectual Property and Copyright Statements . . . . . . . . . . 19

























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1.  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 RFC 2119 [RFC2119].

   This document uses terminology from RFC 2865 [RFC2865] and RFC 2866
   [RFC2866].


2.  Introduction and Rationale

   The remote management Service-Types defined in RFC 2865 [RFC2865]
   include NAS-Prompt and Administrative.  Both of these services
   provide access to the interactive, text-based, Command Line Interface
   (CLI) of the managed entity.  Current deployments of network
   equipment include in the managed entity non-CLI, framed-protocol
   forms of management, such as web browser based management (HTML over
   HTTP), SNMP and NETCONF.  In addition, network devices often support
   more privilege levels for management access than the two levels
   supported by NAS-Prompt (non-privileged) and Administrative
   (privileged).  To address these issues, attributes for framed
   management protocols, management protocol security levels, and
   management access privilege levels are described.


3.  Provisions for Framed Management

   Framed Management means management of an entity by means of a non-
   interactive, non-CLI-style method.  The management information is
   typically formatted in a binary or textual encoding, such as HTML,
   XML or ASN.1/BER.  While remote management by interactive CLI
   sessions is carried over protocols, such as Telnet, Rlogin, and SSH,
   these protocols are primarily for the delivery of terminal, or
   pseudo-TTY services.  Command Line Interface, Menu Interface, or
   other text-based (e.g.  ASCII or UTF-8) terminal emulation interfaces
   are not considered to be Framed Management protocols, as used in this
   document.  Examples of Framed Management protocols include web-based
   management (HTML over HTTP), NETCONF (XML over HTTP/BEEP/SOAP) and
   SNMP (SMI over ASN.1/BER).

   To support the authorization and provisioning of Framed Management
   access to managed entities, this document introduces a new value for
   the Service-Type attribute [RFC2865], and one new attribute.  The new
   value for the Service-Type attribute is Framed-Management.  The
   definition of this service is the provisioning of remote device
   management via a Framed Management protocol, as described in this
   section.  The new attribute is Framed-Management-Protocol, the value



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   of which specifies a particular protocol for use in the remote
   management session.


4.  Provisions for Granular Management Access Rights

   Two new attributes are introduced in this document in support of
   granular management access rights or command privilege levels.

   The Management-Policy-Id attribute is used to contain the name of a
   management access rights policy of local scope.  This attribute
   functions similarly to Filter-ID.  It is a string variable containing
   a policy name of local scope.  The provisioning of the rules invoked
   by application of this management policy is by means outside the
   scope of this document, such as by MIB objects.

   The local application of the Management-Policy-Id within the managed
   entity may take the form of (a) one of an enumeration of command
   privilege levels, (b) a mapping into an SNMP Access Control Model,
   such as the View Based Access Control Model (VACM) table [RFC3415],
   or (c) some other set of management access policy rules that is
   mutually understood by the managed entity and the remote management
   application.  Examples are given in Section 8.

   The Management-Privilege-Level attribute is used to contain an
   Integer-valued management privilege level indication.  This attribute
   serves to modify or augment the management permissions bestowed by
   the NAS-Prompt Service-Type, and thus applies to CLI management
   interfaces.


5.  Provisions for Secure Management Access

   To provide for the authorization and provisioning of secure
   management methods, via a secure transport protocols, one new
   attribute is introduced in this document, Management-Transport-
   Protocol.  The value of this attribute is an enumeration of secure
   transport protocols that may be required for the provisioning of NAS-
   Prompt, Administrative or Framed-Management service.


6.  New Values for Existing RADIUS Attributes

6.1.  Service-Type

   This document defines one new value for an existing RADIUS attribute.
   The Service-Type attribute is defined in Section 5.6 of RFC 2865
   [RFC2865], as follows:



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   This Attribute indicates the type of service the user has requested,
   or the type of service to be provided.  It MAY be used in both
   Access-Request and Access-Accept packets.

   A NAS is not required to implement all of these service types, and
   MUST treat unknown or unsupported Service-Types as though an Access-
   Reject had been received instead.

   A summary of the Service-Type 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     |             Value
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Value (cont)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     Type

         6 for Service-Type.

      Length

         6 Value

         The Value field is four octets.

      This document defines one new value for the Service-Type
      attribute.

      (TBA)     Framed-Management

      The semantics of the Framed-Management service are as follows:

      Framed-Management   A framed management protocol session should
                          be started on the NAS.


7.  New RADIUS Attributes

   This document defines four new RADIUS attributes related to remote
   management authorization.





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7.1.  Framed-Management-Protocol

   The Framed-Management-Protocol attribute indicates the application-
   layer protocol to be used for framed management access.  It MAY be
   used in both Access-Request and Access-Accept packets.  This
   attribute is used in conjunction with a Service-Type of Framed-
   Management.

   A summary of the Framed-Management-Protocol 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     |             Value
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Value (cont)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         (TBA) for Framed-Management-Protocol.

      Length

         6


      Value

         The Value field is four octets.

         1      SNMP
         2      Web-based
         3      NETCONF
         4      FTP
         5      TFTP
         6      CP

   The acronyms used in the above table expand as follows:

   o  SNMP: Simple Network Management Protocol.

   o  Web-based: Use of an embedded web server in the NAS for management
      via a generic web browser client.  The interface presented to the
      administrator may be graphical, tabular or textual.  The protocol
      is HTML over HTTP.




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   o  NETCONF: Management via the NETCONF protocol using XML over
      supported transports (e.g.  HTTP, BEEP, SOAP).

   o  FTP: File Transfer Protocol, used to transfer configuration files
      to and from the NAS.

   o  TFTP: Trivial File Transfer Protocol, used to transfer
      configuration files to and from the NAS.

   o  CP: CP (file copy) protocol, used to transfer configuration files
      to and from the NAS.

7.2.  Management-Transport-Protocol

   The Management-Transport-Protocol attribute indicates the mandated
   transport protocol, usually a secure transport, for use with framed
   or non-framed management access sessions.  It MAY be used in both
   Access-Request and Access-Accept packets.  This attribute MAY be used
   in conjunction with other management access provisioning attributes.

   When a secure form of non-framed management access is specified, for
   example the remote terminal service of Secure Shell (SSH), for access
   to the interactive CLI prompt of the NAS, it means that the terminal
   emulation session is encapsulated in some form of protected
   transport, or tunnel.  It may also mean that an explicit secure mode
   of operation is required, when the terminal emulation access protocol
   contains an intrinsic secure mode of operation.

   When a secure form of framed management access is specified, for
   example SNMP over the Transport Security Model, using SSH, it means
   that the application-layer management protocol is encapsulated in
   some form of protected transport, or tunnel.  It may also mean that
   an explicit secure mode of operation is required, when the framed
   management protocol contains an intrinsic secure mode of operation.

   A value of "Default (1)" indicates that no specific transport
   protocol is being provisioned, and that the NAS should expect the
   default transport associated with application layer protocol to be
   used, or more generally, should accept any supported transport
   protocol.  The same default semantics are conveyed by omitting this
   attribute from an Access-Accept packet.

   A summary of the Management-Transport-Protocol Attribute format is
   shown below.  The fields are transmitted from left to right.







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       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

         (TBA) for Management-Transport-Protocol.

      Length

         6

      Value

         The Value field is four octets.

         1      Default
         2      SSH
         3      TLS
         4      DTLS
         5      BEEP
         6      SOAP

   The acronyms used in the above table expand as follows:

   o  Default: No specific transport is required.  Accept any supported
      transport.

   o  SSH: The Secure Shell protocol.  This refers to the general secure
      transport service of SSH, rather than to the secure remote
      terminal service of SSH.

   o  TLS: Transport Layer Security.

   o  DTLS: Datagram Transport Layer Security.

   o  BEEP: Blocks Extensible Exchange Protocol.

   o  SOAP: Simple Object Access Protocol.

7.3.  Management-Policy-Id

   The Management-Policy-Id attribute indicates the name of the
   management access policy for this user.  Zero or more Management-



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   Policy-Id attributes MAY be sent in an Access-Accept packet.
   Identifying a policy by name allows the policy to be used on
   different NASes without regard to implementation details.

   Multiple forms of management access rules may be expressed by the
   underlying named policy, the definition of which is beyond the scope
   of this document.  The management access policy MAY be applied
   contextually, based on the nature of the management access method.
   For example, some named policies may only be valid for application to
   NAS-Prompt services and some other policies may only be valid for
   application to SMNPv3 services.

   The management access policy named in this attribute, received in an
   Access-Accept packet, MUST be applied to the session authorized by
   the Access-Accept.  If the NAS supports this attribute, but the
   policy name is unknown, or the policy rules are incorrectly
   formatted, the NAS MUST treat the packet as if it had been an Access-
   Reject.

   No precedence relationship is defined for multiple occurrences of the
   Management-Policy-Id attribute.  NAS behavior in such cases is not
   predictable.  Therefore, two or more occurrences of this attribute
   SHOULD NOT be included in a single service provisioning message, such
   as Access-Accept or CoA.

   The content of the Management-Policy-Id attribute is expected to be
   the name of a management access policy of local significance to the
   NAS, within a flat namespace of significance to the NAS.  Overloading
   or subdividing this flat name with multi-part specifiers (e.g.
   Access=remote, Level=7) is likely to lead to poor multi-vendor
   interoperability and SHOULD NOT be utilized.  If a simple flat policy
   name is not sufficient to the anticipated use case, it is RECOMMEDNED
   that a Vendor Specific Attribute be used instead, rather than
   overloading the semantics of Management-Policy-Id.

   A summary of the Management-Policy-Id Attribute format is shown
   below.  The fields are transmitted from left to right.














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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
      |     Type      |    Length     |  Text ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

      Type

         (TBA) for Management-Policy-Id.

      Length

         >= 3

      Text

   The Text field is one or more octets, and its contents are
   implementation dependent.  It is intended to be human readable and
   MUST NOT affect operation of the protocol.  It is recommended that
   the message contain UTF-8 encoded 10646 [RFC3629] characters.

7.4.  Management-Privilege-Level

   The Management-Privilege-Level attribute indicates the integer
   Privilege level to be assigned for management access for the
   authenticated user.  Many NASes provide the notion of differentiated
   management privilege levels denoted by an integer value.  The
   specific access rights conferred by each value are implementation
   dependent.  It MAY be used in both Access-Request and Access-Accept
   packets.

   The management access level indicated in this attribute, received in
   an Access-Accept packet, MUST be applied to the session authorized by
   the Access-Accept.  If the NAS supports this attribute, but the
   privilege level is unknown, the NAS MUST treat the packet as if it
   had been an Access-Reject.

   A summary of the Management-Privilege-Level attribute format is show
   below.  The fields are transmitted from left to right.












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        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

          (TBA) for Management-Privilege-Level.

       Length

          6

       Value

          The Value field is an Integer, denoting a management
          privilege level.


   It is RECOMMENDED to limit this new attribute's use to sessions where
   Service-Type is NAS-Prompt (not Administrative).  Typically, NASes
   treat NAS-Prompt as the minimal privilege CLI service and
   Administrative as full privilege.  Using the Management-Privilege-
   Level attribute with a Service-Type attribute with a value of NAS-
   Prompt will have the effect of increasing the minimum privilege
   level.  Conversely, it is NOT RECOMMENDED to use this attribute with
   a Service-Type of Administrative, which may require decreasing the
   maximum privilege level.


8.  Examples of attribute groupings

   1.  CLI access, via local console or telnet, to the "super-user"
       access level:

       *  Service-Type (6) = Administrative (6)
       *  Management-Transport-Protocol (xx) = Default (1)

   2.  CLI access, via the secure remote terminal service of SSH, to the
       non-privileged user access level:

       *  Service-Type (6) = NAS-Prompt (7)
       *  Management-Transport-Protocol (xx) = SSH (2)





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   3.  CLI access, via the secure remote terminal service of SSH, to a
       custom management access level, defined by a policy:

       *  Service-Type (6) = NAS-Prompt (7)
       *  Transport-Protocol (xx) = SSH (2)
       *  Management-Policy-Id (xx) = "Network Administrator"

   4.  CLI access, via the secure remote terminal service of SSH, with a
       management privilege level of 15:

       *  Service-Type (6) = NAS-Prompt (7)
       *  Management-Transport-Protocol (xx) = SSH (2)
       *  Management-Privilege-Level (xx) = 15

   5.  SNMPv3 access, using an Access Control Model specifier, such as a
       custom VACM View, defined by a policy:

       *  Service-Type (6) = Framed-Management (xx)
       *  Framed-Management-Protocol (xx) = SNMP (1)
       *  Management-Policy-Id (xx) = "SNMP Network Administrator View"

       Note that there is currently no standardized way of implementing
       this management policy mapping within SNMPv3.  Such mechanisms
       are implementation specific.

   6.  SNMP secure Transport Model access, using the Secure Shell
       Transport Model:

       *  Service-Type (6) = Framed-Management (xx)
       *  Framed-Management-Protocol (xx) = SNMP (1)
       *  Transport-Protocol (xx) = SSH (2)

   7.  Web (HTTP) access:

       *  Service-Type (6) = Framed-Management (xx)
       *  Framed-Management-Protocol (xx) = Web-based (2)

   8.  Secure web access, using a custom management access level,
       defined by a policy:

       *  Service-Type (6) = Framed-Management (xx)
       *  Framed-Management-Protocol (xx) = Web-based (2)
       *  Management-Transport-Protocol (xx) = TLS (3)
       *  Management-Policy-Id (xx) = "Read-only web access"







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9.  Diameter Translation Considerations

   When used in Diameter, the attributes defined in this specification
   can be used as Diameter 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|
   ---------------------------------|----+-----+----+-----|----|
   Service-Type (new value)         |    |     |    |     |    |
                         Enumerated | M  |  P  |    |  V  | Y  |
   Framed-Management-Protocol       |    |     |    |     |    |
                         Enumerated | M  |  P  |    |  V  | Y  |
   Management-Transport-Protocol    |    |     |    |     |    |
                         Enumerated | M  |  P  |    |  V  | Y  |
   Management-Policy-Id             |    |     |    |     |    |
                         UTF8String | M  |  P  |    |  V  | Y  |
   Management-Privilege-Level       |    |     |    |     |    |
                         Integer    | 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].

   What is said about Access-Accept applies in Diameter to AA-Answer
   messages that indicate success.


10.  RADIUS Proxy Operation Considerations

   The device management access authorization attributes presented in
   this document present certain considerations when used in RADIUS
   proxy environments.  These considerations are not different from
   those that exist in RFC 2865 [RFC2865] with respect to the Service-



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   Type attribute values of Administrative and NAS-Prompt.

   Most RADIUS proxy environments are also multi-party environments.  In
   multi-party proxy environments it is important to distinguish which
   entities have the authority to provision management access to the
   edge devices, i.e.  NASes, and which entities only have authority to
   provision network access services of various sorts.

   It may be important that operators of the NAS are able to ensure that
   access to the CLI, or other management interfaces, of the NAS are
   only provisioned to their own employees or contractors.  One way for
   the NAS to enforce this requirement is to use only local, non-proxy
   RADIUS servers for management access requests.  Proxy RADIUS servers
   could be used for non-management access requests, based on local
   policy.  This "bifurcation" of RADIUS authentication and
   authorization is a simple case of separate administrative realms.
   The NAS may be designed so as to maintain separate lists of RADIUS
   servers for management AAA use and for non-management AAA use.

   An alternate method of enforcing this requirement would be for the
   first-hop RADIUS proxy server, operated by the owner of the NAS, to
   filter out any RADIUS attributes that provision management access
   rights that originate from "up-stream" proxy servers not operated by
   the NAS owner.  Access-Accept messages that provision such locally
   un-authorized management access MAY be treated as if they were an
   Access-Reject by the first-hop proxy server.

   These issues are not of concern when all the RADIUS servers, local
   and proxy, used by the NAS are under the sole administrative control
   of the NAS owner.


11.  Table of Attributes

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















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   Access-
   Request Accept Reject Challenge  #    Attribute
   ---------------------------------------------------------------------
   0-1     0-1      0        0     TBA   Framed-Management-Protocol
   0-1     0-1      0        0     TBA   Management-Transport-Protocol
   0       0-1      0        0     TBA   Management-Policy-Id
   0       0-1      0        0     TBA   Management-Privilege-Level

   Accounting-
   Request Response  #    Attribute
   ---------------------------------------------------------------------
   0-1     0        TBA   Framed-Management-Protocol
   0-1     0        TBA   Management-Transport-Protocol
   0-1     0        TBA   Management-Policy-Id
   0-1     0        TBA   Management-Privilege-Level

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

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


12.  IANA Considerations

   This document contains placeholders ("TBA") for assigned numbers
   within the RADIUS Attributes registry, to be assigned by IANA at the
   time this document should be published as an RFC.  Assignment of
   additional values for attributes defined in this document are to be
   processed as described in [RFC3575], subject to the additional
   requirement that a published specification is required.


13.  Security Considerations

   This specification describes the use of RADIUS and Diameter for
   purposes of authentication, authorization and accounting for
   management access to devices within 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



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   existing RADIUS packets, which may be 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.

   Any of the attributes described in this memo, with the exception of
   Service-Type, may not be understood by the NAS which receives it.  A
   legacy NAS not compliant with this specification may silently discard
   these attributes while permitting the user to access the management
   interface(s) of the NAS.  This can lead to users improperly receiving
   unauthorized management access to the NAS, or access with greater
   levels of access rights than were intended.  RADIUS servers SHOULD
   attempt to ascertain whether or not the NAS supports these attributes
   before sending them in an Access-Accept.


14.  Acknowledgments

   Many thanks to all reviewers, including Barney Wolff, Mauricio
   Sanchez, David Harrington, Juergen Schoenwaelder, Bernard Aboba.


15.  References

15.1.  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.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

15.2.  Informative References

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

   [RFC2866]  Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.




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   [RFC3415]  Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
              Access Control Model (VACM) for the Simple Network
              Management Protocol (SNMP)", STD 62, RFC 3415,
              December 2002.

   [RFC3575]  Aboba, B., "IANA Considerations for RADIUS (Remote
              Authentication Dial In User Service)", RFC 3575,
              July 2003.

   [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.

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


Authors' Addresses

   David B. Nelson
   Elbrys Networks, Inc.
   75 Rochester Avenue, Unit 3
   Portsmouth, NH  03801
   USA

   Email: d.b.nelson@comcast.net








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   Greg Weber


   Email: gdweber@gmail.com















































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