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Versions: 01 rfc2058                                                    
Network Working Group                                          S Willens
Internet Draft                                                Livingston
                                                                A Rubens
                                                                   Merit
                                                             W A Simpson
                                                              Daydreamer
                                                                C Rigney
                                                              Livingston
expires in six months                                           May 1994


          Remote Authentication Dial In User Service (RADIUS)
                   draft-ietf-nasreq-radius-01.txt (c)



Status of this Memo

   This document is a submission to the Network-Access-Server-
   Requirements Working Group of the Internet Engineering Task Force
   (IETF).  Comments should be submitted to the nas-req@merit.edu
   mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months.  Internet-Drafts may be updated, replaced, or obsoleted by
   other documents at any time.  It is not appropriate to use Internet-
   Drafts as reference material or to cite them other than as a
   ``working draft'' or ``work in progress.''

   To learn the current status of any Internet-Draft, please check the
   1id-abstracts.txt listing contained in the Internet-Drafts Shadow
   Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
   munnari.oz.au.


Abstract

   This document describes a protocol for carrying authentication,
   authorization, and configuration information between a Network Access
   Server which desires to authenticate its links and a shared
   Authentication Server.



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                           Table of Contents


     1.     Introduction ..........................................    1
        1.1       Specification of Requirements ...................    2
        1.2       Terminology .....................................    2

     2.     Operation .............................................    3
        2.1       Challenge/Response ..............................    4

     3.     Packet Format .........................................    5
        3.1       Access-Request ..................................    8
        3.2       Access-Ack ......................................    9
        3.3       Access-Reject ...................................   10
        3.4       Access-Challenge ................................   11

     4.     Attributes ............................................   13
        4.1       User-Name .......................................   14
        4.2       User-Password ...................................   15
        4.3       Challenge-Response ..............................   16
        4.4       NAS-Identifier ..................................   17
        4.5       NAS-Port ........................................   18
        4.6       User-Service ....................................   19
        4.7       Framed-Protocol .................................   19
        4.8       Framed-Address ..................................   20
        4.9       Framed-Netmask ..................................   21
        4.10      Framed-Routing ..................................   22
        4.11      Framed-Filter ...................................   23
        4.12      Framed-MTU ......................................   23
        4.13      Framed-Compression ..............................   24
        4.14      Login-Host ......................................   25
        4.15      Login-Service ...................................   26
        4.16      Login-TCP-Port ..................................   27
        4.17      Change-Password .................................   27
        4.18      Reply-Message ...................................   27
        4.19      Callback-Number .................................   28
        4.20      Callback-Name ...................................   29
        4.21      (unassigned) ....................................   30
        4.22      Framed-Route ....................................   30
        4.23      Framed-IPX-Network ..............................   31
        4.24      State ...........................................   32

     SECURITY CONSIDERATIONS ......................................   33

     REFERENCES ...................................................   34
     ACKNOWLEDGEMENTS .............................................   34

     CHAIR'S ADDRESS ..............................................   35
     AUTHOR'S ADDRESS .............................................   35


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1.  Introduction

   Managing dispersed serial line and modem pools for large numbers of
   users can create the need for significant administrative support.
   Since modem pools are by definition a link to the outside world, they
   require careful attention to security, authorization and accounting.
   This can be best achieved by managing a single "database" of users,
   which allows for authentication (verifying user name and password) as
   well as configuration information detailing the type of service to
   deliver to the user (that is, SLIP, PPP, telnet, rlogin).

   Key features of RADIUS are:

   Client/Server Model

      A Network Access Server (NAS) operates as a client of RADIUS.  The
      NAS is responsible for passing user information to designated
      RADIUS servers, and then acting on the response which is returned.

      RADIUS servers are responsible for receiving user connection
      requests, authenticating the user, and then returning all
      configuration information necessary for the NAS to deliver service
      to the user.

      The RADIUS servers can act as proxy clients to other
      authentication servers, such as Kerberos.

   Network Security

      Transactions between the NAS and RADIUS server are authenticated
      through the use of a shared secret, which is never sent over the
      network.  In addition, any user passwords are sent encrypted
      between the NAS and RADIUS server, to eliminate the possibility
      that someone snooping on an unsecure network could determine a
      user's password.

   Flexible Authentication Mechanisms

      The RADIUS server supports a variety of methods to authenticate a
      user.  When it is provided with the user name and original
      password given by the user, it can support PPP PAP or CHAP, UNIX
      login, and other authentication mechanisms available through
      published API's such as Kerberos and SafeWord.

   Extensible Protocol

      All transactions are comprised of variable length attribute-value
      tuples.  Adding new attribute values can be achieved without



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      disturbing existing implementations of the protocol.

   Source Code Availability

      Livingston Enterprises is making the C source code for RADIUS
      available without use restrictions.


1.1.  Specification of Requirements

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.

   MUST      This word, or the adjective "required", means that the
             definition is an absolute requirement of the specification.

   MUST NOT  This phrase means that the definition is an absolute
             prohibition of the specification.

   SHOULD    This word, or the adjective "recommended", means that there
             may exist valid reasons in particular circumstances to
             ignore this item, but the full implications must be
             understood and carefully weighed before choosing a
             different course.

   MAY       This word, or the adjective "optional", means that this
             item is one of an allowed set of alternatives.  An
             implementation which does not include this option MUST be
             prepared to interoperate with another implementation which
             does include the option.


1.2.  Terminology

   This document frequently uses the following terms:

   silently discard
             This means the implementation discards the packet without
             further processing.  The implementation SHOULD provide the
             capability of logging the error, including the contents of
             the silently discarded packet, and SHOULD record the event
             in a statistics counter.









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2.  Operation

   When a NAS is configured to use RADIUS, any user of the NAS presents
   authentication information to the NAS.  This might be with a
   customizable login prompt, where the user is expected to enter their
   username and password.  Alternatively, the user might use a link
   framing protocol such as the Point-to-Point Protocol (PPP), which has
   authentication packets which carry this information.

   Once the NAS has obtained such information, it first looks in its
   local database of users for the username.  If found, the user is
   locally authenticated.  If not found, the NAS will create an
   "Access-Request" containing such attributes as the user's name, the
   user's password, the ID of the NAS and the Port ID which the user is
   accessing.  When a password is present, it is hidden using a method
   based on the RSA Message Digest Algorithm MD5 [3].

   The Access-Request is submitted to the RADIUS server via the network.
   If no response is returned within a configurable length of time, the
   request is re-sent a configurable number of times.  After several
   failed attempts, the NAS can also forward requests to an alternate
   server in the event that the primary server is down or unreachable.

   Once the RADIUS server receives the request, it validates the sending
   client.  The RADIUS server consults a local database of users to find
   the user whose name matches the request.  The user entry in the
   database contains a list of requirements which must be met to allow
   access for the user.  This always includes verification of the
   password, but can also specify the NAS or Port to which the user is
   allowed access.

   The RADIUS server MAY make requests of other servers in order to
   satisfy the request.

   If any condition is not met, the RADIUS server sends an "Access-
   Reject" response indicating that this user request is invalid.  If
   desired, the server MAY also send a text message which MAY be
   displayed by the NAS to the user.  No other attributes are permitted
   in an "Access-Reject".

   If all conditions are met and the RADIUS server wishes to issue a
   challenge to which the user must respond, the RADIUS server sends an
   "Access-Challenge" response.

   If the NAS receives an Access-Challenge and supports
   challenge/response it MAY display the text message, if any, to the
   user, and then prompt the user for a response.  It then re-submits
   its original Access-Request with a new request ID, with the Password



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   attribute replaced by the response (encrypted), and including the
   State attribute from the "Access-Challenge", if any.  Only 0 or 1
   State attributes should be present in a request.

   If all conditions are met, the list of configuration values for the
   user are placed into an "Access Ack" response.  These values include
   the type of usage (SLIP, PPP, Login User), and all necessary values
   to deliver the desired service.  For SLIP and PPP, this includes such
   values as IP addresses, subnet masks, MTU, desired compression, and
   desired packet filters.  For character mode users, this includes
   things such as desired protocol, host, and access control filter.


2.1.  Challenge/Response

   In challenge/response authentication, individual users are given an
   unpredictable number and challenged to encrypt it and give back the
   result. Authorized users are equipped with special devices such as
   smart cards that facilitate calculation of the correct response with
   ease. Unauthorized users, lacking the appropriate device and lacking
   knowledge of the secret key necessary to emulate such a device, can
   only guess at the response.

   The Access-Challenge packet typically contains a Reply-Message
   including a challenge to be displayed to the user, such as a numeric
   value unlikely ever to be repeated. Typically this is obtained from
   an external server that knows what type of authenticator should be in
   the possession of the authorized user and can therefore choose a
   random or non-repeating pseudorandom number of an appropriate radix
   and length.

   The user then enters the challenge into his device and it calculates
   a response, which the user enters into the NAS which forwards it to
   the RADIUS server via a second Access-Request.  If the response
   matches the expected response the RADIUS server replies with an
   Access-Ack, otherwise an Access-Reject.















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3.  Packet Format

   Exactly one RADIUS packet is encapsulated in the UDP Data field [1],
   where the UDP Destination Port field indicates 1645, and the UDP
   Source Port field is used to indicate the specific request which was
   made.  Each new request MUST use a new UDP Source Port.  A
   retransmitted request does not need to be considered a new request.
   An Access-Request sent in reply to an Access-Challenge does not need
   to be considered a new request and can use the same UDP Source Port
   as the Access-Request that resulted in the Access-Challenge.

   When a reply is generated, the Ports are reversed.

A summary of the RADIUS data 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Code      |  Identifier   |            Length             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                         Authenticator                         |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Attributes ...
+-+-+-+-+-+-+-+-+-+-+-+-+-


Code

   The Code field is one octet, and identifies the type of RADIUS
   packet.  When a packet is received with an invalid Code field, it is
   silently discarded.

   RADIUS Codes (decimal) are assigned as follows:

       1       Access-Request
       2       Access-Ack
       3       Access-Reject
      11       Access-Challenge


Identifier

   The Identifier field is one octet, and aids in matching requests and
   replies.



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Length

   The Length field is two octets.  It indicates the length of the
   packet including the Code, Identifier, Length, Authenticator and
   Attribute fields.  Octets outside the range of the Length field
   should be treated as padding and should be ignored on reception.

Authenticator

   The Authenticator field is sixteen octets.  The most significant
   octet is transmitted first.  This value is used to authenticate the
   reply from the RADIUS server, and is used in the password hiding
   algorithm.

   The Request Authenticator value depends upon the method used to
   generate the octets, and is independent of the hash algorithm used to
   generate any response.  The value SHOULD be unique and unpredictable.

   The Ack, Reject, or Challenge Authenticator field contains a one-way
   MD5 hash calculated over a stream of octets consisting of the RADIUS
   packet, beginning with the Code field, including the Identifier, the
   Length, the Request Authenticator, and the response Attributes,
   followed by (concatenated with) a "shared secret".

   The one-way hash algorithm is chosen such that it is computationally
   infeasible to determine the secret from the known request and
   response values.

   The secret SHOULD be at least as large and unguessable as a well-
   chosen password.  It is preferred that the secret be at least the
   length of the hash value for the hashing algorithm chosen (16 octets
   for MD5).  This is to ensure a sufficiently large range for the
   secret to provide protection against exhaustive search attacks.

   Each Request Authenticator value SHOULD be unique over the lifetime
   of a secret, since repetition of a request value in conjunction with
   the same secret would permit an attacker to reply with a previously
   intercepted response.  Since it is expected that the same secret MAY
   be used to authenticate with servers in disparate geographic regions,
   the request SHOULD exhibit global and temporal uniqueness.

   Each Request Authenticator value SHOULD also be unpredictable, lest
   an attacker trick a server into responding to a predicted future
   request, and then use the response to masquerade as that server to
   another authenticator.

   Although protocols such as RADIUS are incapable of protecting against
   theft of an authenticated session via realtime active wiretapping



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   attacks, generation of unique unpredictable requests can protect
   against a wide range of active attacks against authentication.

















































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3.1.  Access-Request

   Description

      Access-Request packets are sent to a RADIUS server, and convey
      information used to determine whether a user is allowed access to
      a specific NAS, and any special services requested for that user.
      An implementation wishing to Authenticate a user MUST transmit a
      RADIUS packet with the Code field set to 1 (Access-Request).

      Upon receipt of an Access-Request, an appropriate reply MUST be
      transmitted.

      This request MUST contain attributes containing the ID of the NAS
      and the user's name, and SHOULD contain attributes with the user's
      password and the Port ID which the user is accessing.  It MAY
      contain additional attributes as a hint to the server.  When a
      password is present, it is hidden using a method based on the RSA
      Message Digest Algorithm MD5 [3].

   A summary of the Access-Request packet 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |  Identifier   |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Authenticator                         |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Attributes ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-


   Code

      1 for Access-Request.

   Identifier

      The Identifier field MUST be changed whenever the content of the
      Attributes field changes, and whenever a valid reply has been
      received for a previous request.  For retransmissions, the
      Identifier MAY remain unchanged.




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   Authenticator

      The Authenticator value MUST be changed each time a new Identifier
      is used.

   Attributes

      The Attribute field is variable in length, and contains the list
      of attributes that are required for the type of service, as well
      as any desired optional attributes.



3.2.  Access-Ack

   Description

      Access-Ack packets are sent by the RADIUS server, and provide
      specific configuration information necessary to begin delivery of
      services to the user.  If every Attribute received in an Access-
      Request is recognizable and all values are acceptable, then the
      RADIUS implementation MUST transmit a packet with the Code field
      set to 2 (Access-Ack).

      On reception of an Access-Ack, the Identifier field is matched
      with a pending Access-Request.  Additionally, the Authenticator
      field MUST contain the correct response for the pending Access-
      Request.  Invalid packets are silently discarded.

   A summary of the Access-Ack packet 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |  Identifier   |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Authenticator                         |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Attributes ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-







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   Code

      2 for Access-Ack.

   Identifier

      The Identifier field is a copy of the Identifier field of the
      Access-Request which caused this Access-Ack.

   Authenticator

      The Authenticator value is calculated from the Access-Request
      value, as described earlier.

   Attributes

      The Attribute field is variable in length, and contains a list of
      zero or more Attributes.



3.3.  Access-Reject

   Description

      If any value of the received Attributes is not acceptable, then
      the RADIUS server MUST transmit a packet with the Code field set
      to 3 (Access-Reject).  It MAY include a Reply-Message Attribute
      with a text message which the NAS MAY display to the user.

   A summary of the Access-Reject packet 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |  Identifier   |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Authenticator                         |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Attributes ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-






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   Code

      3 for Access-Reject.

   Identifier

      The Identifier field is a copy of the Identifier field of the
      Access-Request which caused this Access-Reject.

   Authenticator

      The Authenticator value is calculated from the Access-Request
      value, as described earlier.

   Attributes

      The Attribute field is variable in length, and contains a list of
      zero or more Attributes.



3.4.  Access-Challenge

   Description

      If the RADIUS server desires to send the user a challenge
      requiring a response, then the RADIUS server MUST respond to the
      Access-Request by transmitting a packet with the Code field
      set to 4 (Access-Challenge).

      The Attributes field MAY have a Reply-Message Attribute.  and MAY
      have a State Attribute.  No other attributes are permitted in an
      Access-Challenge.

      On receipt of an Access-Challenge, the Identifier field is matched
      with a pending Access-Request.  Additionally, the Authenticator
      field MUST contain the correct response for the pending Access-
      Request.  Invalid packets are silently discarded.

      If the NAS supports challenge/response, receipt of a valid
      Access-Challenge indicates that a new Access-Request SHOULD be
      submitted.  The NAS MAY display the text message, if any, to the
      user, and then prompt the user for a response.  It then re-submits
      its original Access-Request with a new request ID, with the
      Password attribute replaced by the user's response (encrypted),
      and including the State attribute from the "Access-Challenge", if
      any.  Only 0 or 1 State attributes should be present in a request.




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      A NAS which supports PAP MAY forward the Reply-Message to the
      dialin client and accept a PAP response which it can use as though
      the user had entered the response.

   A summary of the Access-Challenge packet 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |  Identifier   |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Authenticator                         |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Attributes ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-


   Code

      11 for Access-Challenge.

   Identifier

      The Identifier field is a copy of the Identifier field of the
      Access-Request which caused this Access-Challenge.

   Authenticator

      The Authenticator value is calculated from the Access-Request
      value, as described earlier.

   Attributes

      The Attributes field is variable in length, and contains a list of
      zero or more Attributes.












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4.  Attributes

   RADIUS Attributes carry the specific authentication, authorization,
   information and configuration details for the request and reply.

   Some Attributes MAY be listed more than once.  The effect of this is
   Attribute specific, and is specified by each such Attribute
   description.

   The end of the list of Attributes is indicated by the length of the
   RADIUS packet.

   A summary of the 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  Value ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      The Type field is one octet.  Up-to-date values of the RADIUS Type
      field are specified in the most recent "Assigned Numbers" RFC [2].
      Values 192-223 are reserved for experimental use, values 224-240
      are reserved for implementation-specific use, and values 241-255
      are reserved and should not be used.  This specification concerns
      the following values:

          1      User-Name
          2      User-Password
          3      Challenge-Response
          4      NAS-Identifier
          5      NAS-Port
          6      User-Service
          7      Framed-Protocol
          8      Framed-Address
          9      Framed-Netmask
         10      Framed-Routing
         11      Framed-Filter
         12      Framed-MTU
         13      Framed-Compression
         14      Login-Host
         15      Login-Service
         16      Login-TCP-Port
         17      (deprecated)



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         18      Reply-Message
         19      Callback-Number
         20      Callback-Name
         21      (unassigned)
         22      Framed-Route
         23      Framed-IPX-Network
         24      State

   Length

      The Length field is one octet, and indicates the length of this
      Attribute including the Type, Length and Value fields.  If an
      Attribute is received in a Access-Request but with an invalid
      Length, an Access-Reject SHOULD be transmitted.

   Value

      The Value field is zero or more octets and contains information
      specific to the Attribute.  The format and length of the Value
      field is determined by the Type and Length fields.

      The format of the value field is one of four data types.

      string    0-253 octets

      address   32 bit value, most significant octet first.

      integer   32 bit value, most significant octet first.

      time      32 bit value, most significant octet first -- seconds
                since 00:00:00 GMT, January 1, 1970.



4.1.  User-Name

   Description

      This attribute indicates the name of the user to be authenticated.
      It is only used in Access-Request packets.

   A summary of the User-Name 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     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      1

   Length

      >= 3

   String

      The String field is one or more octets.

      The format of the username may be one of several forms:

      monolithic Consisting only of alphanumeric characters.  This
                simple form might be used to locally manage a NAS.

      provider/name
                Two monolithic portions separated by a slash.  The
                provider part indicates the realm in which the name part
                applies.

      name@fqdn SMTP address.  The Fully Qualified Domain Name (with or
                without trailing dot) indicates the realm in which the
                name part applies.

      distinguished name
                A name in ASN.1 form used in Public Key authentication
                systems.



4.2.  User-Password

   Description

      This attribute indicates the password of the user to be
      authenticated.  It is only used in Access-Request packets.

      On transmission, the password is hidden.  A one-way MD5 hash is



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      calculated over a stream of octets consisting of the "shared
      secret", followed by (concatenated with) the Request
      Authenticator.  This value is xor'd with each successive 16 octet
      segment of the password.

      On receipt, the same mask is created.  Repeating the xor function
      yields the original password.

   A summary of the User-Password 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      2

   Length

      >= 3

   String

      The String field is one or more octets.



4.3.  Challenge-Response

   Description

      This attribute indicates the response value provided by a PPP
      Challenge-Handshake Authentication Protocol (CHAP) user in
      response to the challenge.  It is only used in Access-Request
      packets.

      The CHAP challenge value is found in the RADIUS Authenticator
      field.

   A summary of the Challenge-Response 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 2 3 4 5 6 7 8 9
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  CHAP Ident   |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      3

   Length

      >= 18

   CHAP Ident

      This field is one octet, and contains the CHAP Identifier from the
      CHAP Response packet.

   String

      The String field is 16 octets when MD5 is used for CHAP.



4.4.  NAS-Identifier

   Description

      This attribute indicates the Identifying Address of the NAS which
      is authenticating the user.  It is only used in Access-Request
      packets.

   A summary of the NAS-Identifier 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 (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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   Type

      4

   Length

      6

   Address

      The Address field is four octets.



4.5.  NAS-Port

   Description

      This attribute indicates the port number of the NAS which is
      authenticating the user.  It is only used in Access-Request
      packets.

   A summary of the NAS-Port 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

      5

   Length

      6

   Value

      The Value field is four octets.  Despite the rather large size of
      the field, values range from 0 to 65535.





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4.6.  User-Service

   Description

      This attribute indicates the type of link the user has requested,
      or a change in the type of link to be configured.  It is used in
      both Access-Request and Access-Ack packets.

   A summary of the User-Service 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

   Length

      6

   Value

      The Value field is four octets.

       1      Login
       2      Framed
       3      Callback Login
       4      Callback Framed
       5      Outbound User
       6      Shell User




4.7.  Framed-Protocol

   Description

      This attribute indicates the framing to be used for framed access.
      It is used in both Access-Request and Access-Ack packets.



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   A summary of the Framed-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

      7

   Length

      6

   Value

      The Value field is four octets.

       1      PPP
       2      SLIP




4.8.  Framed-Address

   Description

      This attribute indicates the address to be configured for the
      user.  It is only used in Access-Ack packets.

   A summary of the Framed-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 (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   Type

      8

   Length

      6

   Address

      The Address field is four octets.  The value 0xFFFFFFFF indicates
      that the NAS should allow the user to select an address (e.g.
      Negotiated).  The value 0xFFFFFFFE indicates that the NAS should
      select an address for the user (e.g. Assigned from a pool of
      addresses kept by the NAS).



4.9.  Framed-Netmask

   Description

      This attribute indicates the IP netmask to be configured for the
      user when the user is a router to a network.  It is unnecessary
      when routing is used.  It is only used in Access-Ack packets.

   A summary of the Framed-Netmask 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     |            Netmask
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Netmask (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      9

   Length

      6






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   Netmask

      The Netmask field is four octets.



4.10.  Framed-Routing

   Description

      This attribute indicates the routing method for the user, when the
      user is a router to a network.  It is only used in Access-Ack
      packets.

   A summary of the Framed-Routing 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

      10

   Length

      6

   Value

      The Value field is four octets.

       0      None
       1      Send routing packets
       2      Listen for routing packets
       3      Send and Listen









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4.11.  Framed-Filter

   Description

      This attribute indicates the name of the filter list for this
      user.

      Using a name for a filter list allows independence from multiple
      NAS implementations.  However, the name used might be dependent on
      the NAS making the request, rather than the user.

   A summary of the Framed-Filter 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      11

   Length

      >= 3

   String

      The String field is one or more octets.



4.12.  Framed-MTU

   Description

      This attribute indicates the Maximum Transmission Unit to be
      configured for the user, when it is not negotiated by some other
      means (such as PPP).  It is only used in Access-Ack packets.

   A summary of the Framed-MTU 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

      12

   Length

      6

   Value

      The Value field is four octets.  Despite the rather large size of
      the field, values range from 64 to 65535.



4.13.  Framed-Compression

   Description

      This attribute indicates a compression protocol to be used for the
      link.

      More than one compression protocol attribute MAY be sent.  It is
      the responsibility of the NAS to apply the proper compression
      protocol to appropriate link traffic.

   A summary of the Framed-Compression 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)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   Type

      13

   Length

      6

   Value

      The Value field is four octets.

       1      VJ TCP/IP header compression
       2      IPX header compression




4.14.  Login-Host

   Description

      This attribute indicates the system with which the user is to be
      automatically connected, when the Login-Service attribute is
      listed.  It is only used in Access-Ack packets.

   A summary of the Login-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 (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      14

   Length

      6






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   Address

      The Address field is four octets.  The value 0xFFFFFFFF indicates
      that the NAS SHOULD allow the user to select an address.  The
      value 0 indicates that the NAS SHOULD select a host to connect the
      user to.



4.15.  Login-Service

   Description

      This attribute indicates the service with which the user is to be
      automatically connected.  It is only used in Access-Ack packets.

   A summary of the Login-Service 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

      15

   Length

      6

   Value

      The Value field is four octets.

       0      Telnet
       1      Rlogin
       2      TCP
       3      Portmaster (proprietary)







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4.16.  Login-TCP-Port

   Description

      This attribute indicates the TCP port with which the user is to be
      automatically connected, when the Login-Service attribute is
      listed.  It is only used in Access-Ack packets.

   A summary of the Login-TCP-Port 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

      16

   Length

      6

   Value

      The Value field is four octets.  Despite the rather large size of
      the field, values range from 0 to 65535.



4.17.  Change-Password

   Description

      THIS ATTRIBUTE HAS BEEN DEPRECATED.



4.18.  Reply-Message

   Description

      This attribute indicates text which MAY be displayed to the user.



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      When used in an Access-Ack, it is the success message.

      When used in an Access-Reject, it is the failure message.  It MAY
      indicate a dialog message to prompt the user before another
      Access-Request attempt.

      When used in an Access-Challenge, it MAY indicate a dialog message
      to prompt the user for a response.

      Multiple Reply-Message's MAY be included and if any are displayed,
      they MUST be displayed in the same order as they appear in the
      packet.

   A summary of the Reply-Message 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      18

   Length

      >= 3

   String

      The String 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 displayable ASCII characters 32 through
      126 decimal.  Mechanisms for extension to other character sets are
      the topic of future research.



4.19.  Callback-Number

   Description

      This attribute indicates a dialing string to be used for callback.
      It is used in both Access-Request and Access-Ack packets.



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   A summary of the Callback-Number 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      19

   Length

      >= 3

   String

      The String field is one or more octets.  The actual format of the
      information is site or application specific, and a robust
      implementation SHOULD support the field as undistinguished octets.

      It is intended that only an authorized user will have correct site
      specific information to make use of the Callback.  The
      codification of the range of allowed usage of this field is
      outside the scope of this specification.



4.20.  Callback-Name

   Description

      This attribute indicates the name of a place to be called.  It is
      used in both Access-Request and Access-Ack packets.

   A summary of the Callback-Name 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-





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   Type

      20

   Length

      >= 3

   String

      The String field is one or more octets.  The actual format of the
      information is site or application specific, and a robust
      implementation SHOULD support the field as undistinguished octets.

      It is intended that only an authorized user will have correct site
      specific information to make use of the Callback.  The
      codification of the range of allowed usage of this field is
      outside the scope of this specification.



4.21.  (unassigned)

   Description

      THIS ATTRIBUTE CODE HAS NOT BEEN ASSIGNED.



4.22.  Framed-Route

   Description

      This attribute provides routing information to be configured for
      the user.  It is used in the Access-Ack packet and can appear
      multiple times.

   A summary of the Framed-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     |     String...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-






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   Type

      22

   Length

      >= 3

   String

      The String 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 displayable ASCII characters 32 through 126
      decimal.

      It MAY contain a destination address in dotted quad form, a space,
      a gateway address in dotted quad form, a space, and a decimal
      metric.



4.23.  Framed-IPX-Network

   Description

      This attribute indicates the IPX Network number to be configured
      for the user.  It is used in Access-Ack packets.

   A summary of the Framed-IPX-Network 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

      23

   Length

      6



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   Value

      The Value field is four octets.



4.24.  State

   Description

      This attribute is available to be sent by the server to the client
      in an Access-Challenge and should be sent unmodified from the
      client to the server in an Access-Ack reply to that Challenge.  No
      interpretation by the client should be made.  A packet may have
      only one State attribute.  Usage of the State attribute is
      implementation dependent.

   A summary of the State 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |     Type      |    Length     |  String ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   Type

      20

   Length

      >= 3

   String

      The String field is one or more octets.  The actual format of the
      information is site or application specific, and a robust
      implementation SHOULD support the field as undistinguished octets.

      The codification of the range of allowed usage of this field is
      outside the scope of this specification.








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Security Considerations

   Security issues are the primary topic of this document.

   In practice, within or associated with each RADIUS server, there is a
   database which associates "user" names with authentication
   information ("secrets").  It is not anticipated that a particular
   named user would be authenticated by multiple methods.  This would
   make the user vulnerable to attacks which negotiate the least secure
   method from among a set (such as PAP rather than CHAP).  Instead, for
   each named user there should be an indication of exactly one method
   used to authenticate that user name.  If a user needs to make use of
   different authentication methods under different circumstances, then
   distinct user names SHOULD be employed, each of which identifies
   exactly one authentication method.

   Passwords and other secrets should be stored at the respective ends
   such that access to them is as limited as possible.  Ideally, the
   secrets should only be accessible to the process requiring access in
   order to perform the authentication.

   The secrets should be distributed with a mechanism that limits the
   number of entities that handle (and thus gain knowledge of) the
   secret.  Ideally, no unauthorized person should ever gain knowledge
   of the secrets.  It is possible to achieve this with SNMP Security
   Protocols [4], but such a mechanism is outside the scope of this
   specification.

   Other distribution methods are currently undergoing research and
   experimentation.  The SNMP Security document [4] also has an
   excellent overview of threats to network protocols.




















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References

   [1]   Postel, J., "User Datagram Protocol", RFC 768, USC/Information
         Sciences Institute, August 1980.

   [2]   Reynolds, J., and J. Postel, "Assigned Numbers", RFC 1340,
         USC/Information Sciences Institute, July 1992.

   [3]   Rivest, R., and S. Dusse, "The MD5 Message-Digest Algorithm",
         MIT Laboratory for Computer Science and RSA Data Security,
         Inc., RFC 1321, April 1992.

   [4]   Galvin, J., McCloghrie, K., and J. Davin, "SNMP Security
         Protocols", Trusted Information Systems, Inc., Hughes LAN
         Systems, Inc., MIT Laboratory for Computer Science, RFC 1352,
         July 1992.



Acknowledgments

   RADIUS was originally developed by Livingston Enterprises for their
   PortMaster series of Network Access Servers.




























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Chair's Address

   The working group can be contacted via the current chair:

      John Vollbrecht
      Merit Network, Inc.
      1071 Beal Ave.
      Ann Arbor, MI 48109

      EMail: jrv@merit.edu


Author's Address

   Questions about this memo can also be directed to:

      Steve Willens
      Livingston Enterprises
      6920 Koll Center Parkway, Suite 220
      Pleasanton, CA  94566

      EMail: steve@livingston.com

      Allan C. Rubens
      Merit Network, Inc.
      1071 Beal Ave.
      Ann Arbor, MI 48109

      EMail: acr@merit.edu

      William Allen Simpson
      Daydreamer
      Computer Systems Consulting Services
      1384 Fontaine
      Madison Heights, Michigan  48071

      EMail: Bill.Simpson@um.cc.umich.edu

      Carl Rigney
      Livingston Enterprises
      6920 Koll Center Parkway, Suite 220
      Pleasanton, CA  94566

      EMail: cdr@livingston.com







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