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Versions: 00 01 02 03 04 05 06 07 08                                    
INTERNET DRAFT                                            Pat R. Calhoun
Category: Standards Track                          Sun Microsystems, Inc.
Title: draft-calhoun-diameter-authent-04.txt              William Bulley
Date: July 1998                                       Merit Network, Inc.



                                DIAMETER
                     User Authentication Extensions
                <draft-calhoun-diameter-authent-04.txt>



Status of this Memo

   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
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as ``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 ftp.is.co.za (Africa), nic.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or
   ftp.isi.edu (US West Coast).


Abstract

   DIAMETER is a Policy and AAA protocol which can be used for a variety
   of services. This document defines DIAMETER messages that are used
   for the authentication, authorization and accounting of users.

   A considerable amount of effort was put into the design of this
   protocol to ensure that an implementation could support both DIAMETER
   and RADIUS concurrently.










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Table of Contents

      1.0  Introduction
      1.1  Specification of Requirements
      2.0  Command Codes
      2.1  Domain-Discovery-Request
      2.2  Domain-Discovery-Answer
      2.3  AA-Request
      2.4  AA-Answer
      2.5  AA-Challenge-Ind
      3.0  DIAMETER AVPs
      3.1  User-Name
      3.2  User-Password
      3.3  CHAP-Password
      3.4  NAS-Port
      3.5  Service-Type
      3.6  Framed-Protocol
      3.7  Framed-IP-Address
      3.8  Framed-IP-Netmask
      3.9  Framed-Routing
      3.10 Filter-Id
      3.11 Framed-MTU
      3.12 Framed-Compression
      3.13 Login-IP-Host
      3.14 Login-Service
      3.15 Login-TCP-Port
      3.16 Reply-Message
      3.17 Callback-Number
      3.18 Callback-Id
      3.19 Framed-Route
      3.20 Framed-IPX-Network
      3.21 State
      3.22 Class
      3.23 Vendor-Specific
      3.24 Session-Timeout
      3.25 Idle-Timeout
      3.26 Termination-Action
      3.27 Called-Station-Id
      3.28 Calling-Station-Id
      3.29 Proxy-State
      3.30 Login-LAT-Service
      3.31 Login-LAT-Node
      3.32 Login-LAT-Group
      3.33 Framed-AppleTalk-Link
      3.34 Framed-AppleTalk-Network
      3.35 Framed-AppleTalk-Zone
      3.36 CHAP-Challenge
      3.37 NAS-Port-Type



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      3.38 Port-Limit
      3.39 Login-LAT-Port
      3.40 Filter-Rule
      3.41 Framed-Password-Policy
      3.42 Table of Attributes
      4.0  Protocol Definition
      4.1  Feature Advertisement/Discovery
      4.2  Authorization Procedure
      4.3  Integration with Resource-Management
      4.4  RADIUS Proxies
      4.5  DIAMETER Proxies
      4.6  Domain Discovery
      5.0  References
      6.0  Acknowledgements
      7.0  Authors' Addresses


1.0  Introduction

   This document describes the DIAMETER User Authentication Extensions
   that can be used for a variety of services including Dial-up users
   via NAS, WWW User Authentication, Firewall User Authentication[5][6].

   This document describes Authentication/Authorization messages as well
   as a set of messages which allow DIAMETER hosts to bypass proxies.

   Since Most of the AVPs found in this document was copied from the
   RADIUS protocol[1], it is possible to have both RADIUS and DIAMETER
   servers read the same dictionary and users files. The backward
   compatibility that DIAMETER offers is intended to facilitate
   deployment.

   The Extension number for this draft is two (2). This value is used in
   the Extension-Id AVP as defined in [2].


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.




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    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.


2.0  Command Codes

   This document defines the following DIAMETER Commands. All DIAMETER
   implementations supporting this extension MUST support all of the
   following commands:

      Command Name          Command Code
      -----------------------------------
      Domain-Discovery-Request  261
      Domain-Discovery-Answer   262
      AA-Request                263
      AA-Answer                 264
      AA-Challenge-Ind          265


2.1  Domain-Discovery-Request (DDR)

   Description

      The Domain-Discovery-Request message is used by a DIAMETER device
      wishing to get contact information about a domain's home
      authentication server as well as to receive password policy
      information. This message MUST contain the User-Name attribute in
      order to pass along the user's domain information.

      The X509-Certificate or the X509-Certificate-URL [2] MUST be
      present in this message in order to inform the home authentication
      server of the issuing host's certificate.

   Message Format

      <Domain-Discovery-Req> ::= <DIAMETER Header>
                                 <Domain-Discovery-Req Command AVP>
                                 <Host-IP-Address AVP>
                                 [<Host-Name AVP>]



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                                 <User-Name AVP>
                                 [<X509-Certificate AVP>]
                                 [<X509-Certificate-URL AVP>]
                                 <Timestamp AVP>
                                 <Initialization-Vector AVP>
                                 {<Integrity-Check-Vector AVP> ||
                                  <Digital-Signature AVP }

   AVP Format

      A summary of the Domain-Discovery-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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           AVP Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          AVP Length           |     Reserved      |U|T|V|E|H|M|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Command Code                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Code

         256     DIAMETER Command

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Command Type

         The Command Type field MUST be set to 261 (Domain-Discovery-
         Request).


2.2  Domain-Discovery-Answer (DDA)

   Description

      The Domain-Discovery-Answer message is sent in response to the



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      Domain-Discovery-Request message by the domain's Home
      authentication server. The message MUST contain either the Host-
      Name or Host-IP-Address and either the X509-Certificate or the
      X509-Certificate-URL attribute and SHOULD contain at least one
      Framed-Password-Policy AVP.

      The absence of any Framed-Password-Policy AVPs means that the
      issuer will only accept CHAP and PAP.

      The Domain-Discovery-Answer message MUST include the Result-Code
      AVP to indicate whether the request was successful or not. The
      following Error Codes are defined for this command:

         DIAMETER_ERROR_UNKNOWN_DOMAIN       1
            This error code is used to indicate to the initiator of the
            request that the requested domain is unknown and cannot be
            resolved.

         DIAMETER_ERROR_BAD_CERT             2
            This error code is used to indicate that the X509-
            Certificate or the X509-Certificate-URL in the Domain-
            Discovery-Request was invalid.

         DIAMETER_ERROR_CANNOT_REPLY         3
            This error code is returned when either an intermediate
            DIAMETER node or the home authentication server cannot reply
            to DIAMETER messages directly.  This could be that the
            policy of an intermediate DIAMETER server does not permit
            direct contact and therefore requires proxying. It could
            also signify that the home authentication server does not
            have public key support.

   Message Format

      <Domain-Discovery-Answer> ::= <DIAMETER Header>
                                    <Domain-Disc-Answer Command AVP>
                                    <Host-IP-Address AVP>
                                    [<Host-Name AVP>]
                                    <Framed-Password-Policy AVP>
                                    [<X509-Certificate AVP>]
                                    [<X509-Certificate-URL AVP>]
                                    <Timestamp AVP>
                                    <Initialization-Vector AVP>
                                    {<Integrity-Check-Vector AVP> ||
                                     <Digital-Signature AVP }

   AVP Format




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      A summary of the Domain-Discovery-Answer 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           AVP Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          AVP Length           |     Reserved      |U|T|V|E|H|M|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Command Code                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Code

         256     DIAMETER Command

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Command Type

         The Command Type field MUST be set to 262 (Domain-Discovery-
         Answer).


2.3  AA-Request (AAR)

   Description

      The AA-Request message is used in order to request authentication
      and authorization for a given user.

      If Authentication is requested the User-Name attribute MUST be
      present. If only Authorization is required it is possible to
      authorize based on DNIS and ANI instead. However, it is not
      possible to authenticate using a User-Name AVP and later
      requesting authorization based on DNIS using the same Session-Id
      (although the inverse is legal).

      Note that the flag field MAY be used in this command in order to



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      indicate that either Authentication-Only or Authorization-Only is
      required for the request. If the Authentication-Only bit is set
      the response MUST NOT include any authorization information. Both
      the Authenticate and Authorize bits MUST NOT be set at the same
      time. To ensure that a user is both authenticated and authorized,
      neither flag is set.

      The AA-Request message MUST include a unique Session-Id AVP. If
      The AA-Request is a result of a successful AA-Challenge-Ind the
      Session-Id MUST be identical to the one provided in the initial
      AA-Request.

   Message Format

      Section 3.42 contains a complete list of all valid AVPs for this
      message.

      <AA-Request> ::= <DIAMETER Header>
                       <AA-Request Command AVP>
                       <Session-Id AVP>
                       <Host-IP-Address AVP>
                       [<Host-Name AVP>]
                       {<User-Name AVP> ||
                        <Called-Station-Id AVP }
                       <Miscellaneous AVPs>
                       <Timestamp AVP>
                       <Initialization-Vector AVP>
                       {<Integrity-Check-Vector AVP> ||
                        <Digital-Signature AVP }

   AVP Format

      A summary of the AA-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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           AVP Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          AVP Length           |     Reserved      |U|T|V|E|H|M|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Command Code                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Code

         256     DIAMETER Command



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      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The AVP Flags field MUST have bit one (Mandatory Support) set.
         In addition, the following bits may be used (note these bits
         are mutually exclusive):

            Authenticate-Only       32
               The Authentication-Only bit is set to indicate that only
               authentication of the user is requested and that no
               authorization information should be returned in the
               response.

            Authorize-Only          64
               The Authorization-Only bit is set to indicate that only
               authorization of the user is requested and that no
               authentication is required.

      Command Type

         The Command Type field MUST be set to 263 (AA-Request).


2.4  AA-Answer (AAA)

   Description

      The AA-Answer message is used in order to indicate that
      Authentication and/or authorization was successful. If
      authorization was requested a list of AVPs with the authorization
      information MUST be attached to the message (see section 3.42).

      The AA-Answer message MUST include the Session-Id AVP that was
      present in the AA-Request. The AA-Answer MUST also include the
      Host-Name AVP and the Result-Code AVP to indicate the status of
      the session. The following error codes are defined for this
      message:

         DIAMETER_ERROR_UNKNOWN_DOMAIN       1
            This error code is used to indicate to the initiator of the
            request that the requested domain is unknown and cannot be
            resolved.

         DIAMETER_ERROR_USER_UNKNOWN         2
            This error code is used to indicate to the initiator that



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            the username request is not valid.

         DIAMETER_ERROR_BAD_PASSWORD         3
            This error code indicates that the password provided is
            invalid.

         DIAMETER_ERROR_CANNOT_AUTHORIZE     4
            This error code is used to indicate that the user cannot be
            authorized due to the fact that the user has expended the
            servers local resources.  This could be a result that the
            server believes that the user already has an active session,
            or that the user has already spent the number of credits in
            his/her account, etc.

      Note that the flag field MUST be set to the same value that was
      found in the AA-Request message.

   Message Format

      Section 3.42 contains a complete list of all valid AVPs for this
      message.

      <AA-Answer> ::= <DIAMETER Header>
                       <AA-Answer Command AVP>
                       <Session-Id AVP>
                       <Result-Code AVP>
                       <Host-IP-Address AVP>
                       [<Host-Name AVP>]
                       <Miscellaneous AVPs>
                       <Timestamp AVP>
                       <Initialization-Vector AVP>
                       {<Integrity-Check-Vector AVP> ||
                        <Digital-Signature AVP }

   AVP Format

      A summary of the AA-Answer 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           AVP Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          AVP Length           |     Reserved      |U|T|V|E|H|M|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Command Code                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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      Code

         256     DIAMETER Command

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The AVP Flags field MUST have bit one (Mandatory Support) set.
         In addition, the following bits may be used (note these bits
         are mutually exclusive):

            Authenticate-Only       32
               The Authentication-Only bit is set to indicate that only
               authentication of the user is requested and that no
               authorization information should be returned in the
               response.

            Authorize-Only          64
               The Authorization-Only bit is set to indicate that only
               authorization of the user is requested and that no
               authentication is required.

      Command Type

         The Command Type field MUST be set to 264 (AA-Answer).


2.5  AA-Challenge-Ind (AACI)

   Description

      If the DIAMETER server desires to send the user a challenge
      requiring a response, then the DIAMETER server MUST respond to the
      AA-Request by transmitting a packet with the Code field set to 265
      (AA-Challenge-Ind).

      The message MAY have one or more Reply-Message AVP, and MAY have a
      single State AVP, or none.  No other AVPs are permitted in an AA-
      Challenge-Ind other than the Integrity-Check-Vector or Digital-
      Signature AVP as defined in [2].

      On receipt of an AA-Challenge-Ind, the Identifier field is matched
      with a pending AA-Request. Invalid packets are silently discarded.

      The receipt of a valid AA-Challenge-Ind indicates that a new AA-



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      Request SHOULD be sent. The NAS MAY display the text message, if
      any, to the user, and then prompt the user for a response.  It
      then sends its original Acess-Request with a new request ID, with
      the User-Password AVP replaced by the user's response (encrypted),
      and including the State AVP from the AA-Challenge-Ind, if any.
      Only zero or one instances of the State Attribute can be present
      in an AA-Request.

      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.  If the NAS cannot do so, it
      should treat the AA-Challenge-Ind as though it had received an
      AA-Answer with a Result-Code AVP set to a value other than
      DIAMETER_SUCCESS instead.

      It is preferable to use EAP [5] instead of the AA-Challenge-Ind,
      yet it has been maintained for backward compatibility.

      The AA-Challenge-Ind message MUST include the Session-Id AVP that
      was present in the AA-Request and MUST include the same flag value
      that was found in the AA-Request.

      Section 3.42 contains a complete list of all valid AVPs for this
      message.

      AA-Challenge-Ind ::= <DIAMETER Header>
                           <AA-Challenge-Ind Command AVP>
                           <Session-Id AVP>
                           <Result-Code AVP>
                           <Host-IP-Address AVP>
                           [<Host-Name AVP>]
                           <Reply-Message AVPs>
                           <Timestamp AVP>
                           <Initialization-Vector AVP>
                           {<Integrity-Check-Vector AVP> ||
                            <Digital-Signature AVP }

   AVP Format

      A summary of the AA-Challenge-Ind 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           AVP Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          AVP Length           |     Reserved      |U|T|V|E|H|M|



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       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Command Code                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Code

         256     DIAMETER Command

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The AVP Flags field MUST have bit one (Mandatory Support) set.
         In addition, following bits may be used (note these bits are
         mutually exclusive):

            Authenticate-Only       32
               The Authentication-Only bit is set to indicate that only
               authentication of the user is requested and that no
               authorization information should be returned in the
               response.

            Authorize-Only          64
               The Authorization-Only bit is set to indicate that only
               authorization of the user is requested and that no
               authentication is required.

      Command Type

         The Command Type field MUST be set to 265 (AA-Challenge-Ind).


3.0  DIAMETER AVPs

   This section will define the mandatory AVPs which MUST be supported
   by all DIAMETER implementations supporting this extension. The
   following AVPs are defined in this document:

      Attribute Name       Attribute Code
      -----------------------------------
      User-Name                   1
      User-Password               2
      CHAP-Password               3
      NAS-IP-Address              4
      NAS-Port                    5
      Service-Type                6



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      Framed-Protocol             7
      Framed-IP-Address           8
      Framed-IP-Netmask           9
      Framed-Routing             10
      Filter-Id                  11
      Framed-MTU                 12
      Framed-Compression         13
      Login-IP-Host              14
      Login-Service              15
      Login-TCP-Port             16
      Reply-Message              18
      Callback-Number            19
      Callback-Id                20
      Framed-Route               22
      Framed-IPX-Network         23
      State                      24
      Class                      25
      Vendor-Specific            26
      Session-Timeout            27
      Idle-Timeout               28
      Termination-Action         29
      Called-Station-Id          30
      Calling-Station-Id         31
      NAS-Identifier             32
      Proxy-State                33
      Login-LAT-Service          34
      Login-LAT-Node             35
      Login-LAT-Group            36
      Framed-AppleTalk-Link      37
      Framed-AppleTalk-Network   38
      Framed-AppleTalk-Zone      39
      CHAP-Challenge             60
      NAS-Port-Type              61
      Port-Limit                 62
      Login-LAT-Port             63
      Filter-Rule               280
      Framed-Password-Policy    281


3.1  User-Name

   Description

      This Attribute indicates the name of the user to be authenticated.
      It is normally used in AA-Request packets, but MAY be present in
      the AA-Answer message.

      A summary of the User-Name Attribute format is shown below. The



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      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         1 for User-Name.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' MAY be set, but the 'E' bit
         MUST NOT be set since proxy servers would have no knowledge of
         the user's domain. The 'V', 'T' and the 'U' bits MUST NOT be
         set.

      String

         The String field is one or more octets. All DIAMETER systems
         SHOULD support User-Name lengths of at least 63 octets. The
         format of the User-Name SHOULD follow the format defined in
         [3].


3.2  User-Password

   Description

      This Attribute indicates the password of the user to be
      authenticated, or the user's input following an AA-Challenge.  It
      is only used in AA-Request packets.

      This AVP MUST be encrypted using one of the methods described in
      [2]. The use of this AVP with shared secret encryption is strongly
      discouraged by the author due to the security implications in a



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      proxy environment, yet the support of this attribute has been
      retained for RADIUS backward compability.

      A summary of the User-Password Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         2 for User-Password.

      AVP Length

         The length of this attribute MUST be at least 24 and MUST be no
         larger than 136.

      AVP Flags

         The 'M' bit MUST be set. Either the 'H' or the 'E' bit MUST be
         set depending upon the security model used. The 'V', 'T' and
         the 'U' bits MUST NOT be set.

         The AVP Flags field MUST have bit one (Mandatory Support) set.
         One of the AVP Encryption bits MUST be set.

      Data

         The Data field is between 16 and 128 octets long, inclusive.


3.3  CHAP-Password

   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 AA-Request packets.



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      If the CHAP-Password Attribute is found in a message, the CHAP-
      Challenge Attribute (60) MUST be present as well.

      A summary of the CHAP-Password Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  CHAP Ident   |    Data ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         3 for CHAP-Password.

      AVP Length

         The length of this attribute MUST be 25.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      CHAP Ident

         This field is one octet, and contains the CHAP Identifier from
         the user's CHAP Response.

      Data

         The Data field is 16 octets, and contains the CHAP Response
         from the user.


3.4  NAS-Port

   Description

      This Attribute indicates the physical port number of the NAS which



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      is authenticating the user. It is normally only used in AA-Request
      messages (see section x for more info). Note that this is using
      "port" in its sense of a physical connection on the NAS, not in
      the sense of a TCP or UDP port number. Either NAS-Port or NAS-
      Port-Type (61) or both SHOULD be present in an AA-Request packet,
      if the NAS differentiates among its ports.

      A summary of the NAS-Port Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         5 for NAS-Port.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets.


3.5  Service-Type

   Description

      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 AA-Request and AA-Answer messages. A NAS is not required



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      to implement all of these service types, and MUST treat unknown or
      unsupported Service-Types as though an AA-Answer with a Result-
      Code other than DIAMETER-SUCCESS had been received instead.

      A summary of the Service-Type Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         6 for Service-Type.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      AVP Length

         The length of this attribute MUST be 12.

      Integer32

         The Integer32 field is four octets.

            1      Login
            2      Framed
            3      Callback Login
            4      Callback Framed
            5      Outbound
            6      Administrative
            7      NAS Prompt
            8      Authenticate Only
            9      Callback NAS Prompt

            The service types are defined as follows when used in an



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            AA-Answer. When used in an AA-Request, they should be
            considered to be a hint to the DIAMETER server that the NAS
            has reason to believe the user would prefer the kind of
            service indicated, but the server is not required to honor
            the hint.

            Login               The user should be connected to a host.

            Framed              A Framed Protocol should be started for
                                the User, such as PPP or SLIP.

            Callback Login      The user should be disconnected and
                                calledback, then connected to a host.

            Callback Framed     The user should be disconnected and
                                called back, then a Framed Protocol
                                should be started for the User, such as
                                PPP or SLIP.

            Outbound            The user should be granted access to
                                outgoing devices.

            Administrative      The user should be granted access to the
                                administrative interface to the NAS from
                                which privileged commands can be
                                executed.

            NAS Prompt          The user should be provided a command
                                prompt on the NAS from which non-
                                privileged commands can be executed.

            Authenticate Only   Only Authentication is requested, and no
                                authorization information needs to be
                                returned in the AA-Answer (typically
                                used by proxy servers rather than the
                                NAS itself).This SHOULD NOT be used in
                                DIAMETER, yet it is maintained for
                                backward compatibility.

            Callback NAS Prompt The user should be disconnected and
                                called back, then provided a command
                                prompt on the NAS from which non-
                                privileged commands can be executed.


3.6  Framed-Protocol

   Description



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      This Attribute indicates the framing to be used for framed access.
      It MAY be used in both AA-Request and AA-Answer messages.

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

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         7 for Framed-Protocol.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets.

            1      PPP
            2      SLIP
            3      AppleTalk Remote Access Protocol (ARAP)
            4      Gandalf proprietary SingleLink/MultiLink protocol
            5      Xylogics proprietary IPX/SLIP


3.7  Framed-IP-Address

   Description

      This Attribute indicates the address to be configured for the



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      user. It MAY be used in AA-Request messages as a hint by the NAS
      to the server that it would prefer that address, but the server is
      not required to honor the hint.

      A summary of the Framed-IP-Address Attribute format is shown
      below.  The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Address                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         8 for Framed-IP-Address.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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). Other valid values
         indicate that the NAS should use that value as the user's IP
         address.


3.8  Framed-IP-Netmask

   Description




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      This Attribute indicates the IP netmask to be configured for the
      user when the user is a router to a network. It MUST be used in
      AA-Answer messages if the Framed-IP-Address AVP was returned with
      a value other than 0xFFFFFFFF. It MAY be used in an AA-Request
      message as a hint by the NAS to the server that it would prefer
      that netmask, but the server is not required to honor the hint.

      A summary of the Framed-IP-Netmask Attribute format is shown
      below.  The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Address                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         9 for Framed-IP-Netmask.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Address

         The Address field is four octets specifying the IP netmask of
         the user.


3.9  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 AA-Answer



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      messages.

      A summary of the Framed-Routing Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Integer32                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         10 for Framed-Routing.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets.

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


3.10  Filter-Id

   Description

      This Attribute indicates the name of the filter list for this
      user. Zero or more Filter-Id attributes MAY be sent in an AA-
      Answer message.



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      Identifying a filter list by name allows the filter to be used on
      different NASes without regard to filter-list implementation
      details. However, this AVP is not roaming friendly since filter
      naming differs from one service provider to another.

      It is strongly encouraged to support the Filter-Rule AVP instead.

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

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         11 for Filter-Id.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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 from the range 32 through 126 decimal.


3.11  Framed-MTU

   Description



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      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 AA-Answer messages.

      A summary of the Framed-MTU Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         12 for Framed-MTU.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets. Despite the size of the
         field, values range from 64 to 65535.


3.12  Framed-Compression

   Description

      This Attribute indicates a compression protocol to be used for the
      link. It MAY be used in AA-Answer packets. It MAY be used in an
      AA-Request packet as a hint to the server that the NAS would
      prefer to use that compression, but the server is not required to
      honor the hint.



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      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.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         13 for Framed-Compression.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets.

            0      None
            1      VJ TCP/IP header compression [7]
            2      IPX header compression


3.13  Login-IP-Host

   Description

      This Attribute indicates the system with which to connect the
      user, when the Login-Service Attribute is included. It MAY be used



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      in AA-Answer messages. It MAY be used in an AA-Request message as
      a hint to the server that the NAS would prefer to use that host,
      but the server is not required to honor the hint.

      A summary of the Login-IP-Host Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Address                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         14 for Login-IP-Host.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Address

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


3.14  Login-Service

   Description

      This Attribute indicates the service which should be used to
      connect the user to the login host. It is only used in AA-Answer



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      messages.

      A summary of the Login-Service Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         15 for Login-Service.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets.

            0      Telnet
            1      Rlogin
            2      TCP Clear
            3      PortMaster (proprietary)
            4      LAT


3.15  Login-TCP-Port

   Description

      This Attribute indicates the TCP port with which the user is to be
      connected, when the Login-Service Attribute is also present. It is



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      only used in AA-Answer packets.

      A summary of the Login-TCP-Port Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         16 for Login-TCP-Port.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets. Despite the size of the
         field, values range from zero to 65535.


3.16  Reply-Message

   Description

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

      When used in an AA-Answer message with a successful Result-Code
      AVP it indicates the success message. When found in the same
      message with a Result-Code other than DIAMETER-SUCCESS it contains
      the failure message.




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      It MAY indicate a dialog message to prompt the user before another
      AA-Request attempt.

      When used in an AA-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.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         18 for Reply-Message.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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 from the range 10, 13, and 32 through 126 decimal.
         Mechanisms for extension to other character sets are beyond the
         scope of this specification.



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3.17  Callback-Number

   Description

      This Attribute indicates a dialing string to be used for callback.
      It MAY be used in AA-Answer packets. It MAY be used in an AA-
      Request packet as a hint to the server that a Callback service is
      desired, but the server is not required to honor the hint.

      A summary of the Callback-Number Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         19 for Callback-Number.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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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3.18  Callback-Id

   Description

      This Attribute indicates the name of a place to be called, to be
      interpreted by the NAS. It MAY be used in AA-Answer messages.

      This AVP is not roaming friendly since it assumes that the
      Callback-Id is configured on the NAS. It is therefore preferable
      to use the Callback-Number AVP instead.

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

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         20 for Callback-Id.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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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3.19  Framed-IP-Route

   Description

      This Attribute provides routing information to be configured for
      the user on the NAS. It is used in the AA-Answer message and can
      appear multiple times.

      A summary of the Framed-Route Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         22 for Framed-IP-Route.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         It MUST contain a destination prefix in dotted quad form
         optionally followed by a slash and a decimal length specifier
         stating how many high order bits of the prefix should be used.
         That is followed by a space, a gateway address in dotted quad
         form, a space, and one or more metrics separated by spaces. For
         example, "192.168.1.0/24 192.168.1.1 1".

         The length specifier may be omitted in which case it should
         default to 8 bits for class A prefixes, 16 bits for class B



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         prefixes, and 24 bits for class C prefixes. For example,
         "192.168.1.0 192.168.1.1 1".

         Whenever the gateway address is specified as "0.0.0.0" the IP
         address of the user SHOULD be used as the gateway address.


3.20  Framed-IPX-Network

   Description

      This Attribute indicates the IPX Network number to be configured
      for the user. It is used in AA-Answer messages.

      A summary of the Framed-IPX-Network Attribute format is shown
      below.  The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         23 for Framed-IPX-Network.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 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



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         the NAS should select an address for the user (e.g. assigned
         from a pool of one or more IPX networks kept by the NAS). Other
         values should be used as the IPX network for the link to the
         user.

3.21  State

   Description

      This Attribute is available to be sent by the server to the client
      in an AA-Challenge and MUST be sent unmodified from the client to
      the server in the new AA-Request reply to that challenge, if any.

      In either usage, 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.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         24 for State.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String




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         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.


3.22  Class

   Description

      This Attribute is available to be sent by the server to the client
      in an AA-Answer and should be sent unmodified by the client to the
      accounting server as part of the Accounting-Request message if
      accounting is supported. No interpretation by the client should be
      made.

      A summary of the Class Attribute format is shown below. The fields
      are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         25 for Class.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.




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      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.


3.23  Vendor-Specific

   Description

      This AVP is not supported in DIAMETER. Vendor Specific Attributes
      are used by enabling the Vendor-Specific bit in the AVP header.


3.24  Session-Timeout

      Description

         This Attribute sets the maximum number of seconds of service to
         be provided to the user before termination of the session or
         prompt.  This Attribute is available to be sent by the server
         to the client in an AA-Answer or AA-Challenge.

         A summary of the Session-Timeout Attribute format is shown
         below.  The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         27 for Session-Timeout.

      AVP Length



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         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is 4 octets, containing a 32-bit unsigned
         integer with the maximum number of seconds this user should be
         allowed to remain connected by the NAS.

         A value of zero means that this session has an unlimited number
         of seconds before termination or prompt.

3.25  Idle-Timeout

   Description

      This Attribute sets the maximum number of consecutive seconds of
      idle connection allowed to the user before termination of the
      session or prompt. This Attribute is available to be sent by the
      server to the client in an AA-Answer or AA-Challenge.

      A summary of the Idle-Timeout Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         28 for Idle-Timeout.

      AVP Length

         The length of this attribute MUST be 12.



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      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is 4 octets, containing a 32-bit unsigned
         integer with the maximum number of consecutive seconds of idle
         time this user should be permitted before being disconnected by
         the NAS.


3.26. Termination-Action

   Description

      This Attribute is not supported in DIAMETER.


3.27  Called-Station-Id

   Description

      This Attribute allows the NAS to send in the AA-Request message
      the phone number that the user called, using Dialed Number
      Identification (DNIS) or similar technology. Note that this may be
      different from the phone number the call comes in on. It is only
      used in AA-Request packets.

      If the Authorization-Only flag is set in the message and the
      User-Name AVP is absent, the DIAMETER Server MUST perform
      authorization based on this field. This can be used by a NAS to
      request whether a call should be answered based on the DNIS.

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

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         30 for Called-Station-Id.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         The String field is one or more octets, containing the phone
         number that the user's call came in on.

         The actual format of the information is site or application
         specific. Printable ASCII is recommended, but 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.


3.28  Calling-Station-Id

   Description

      This Attribute allows the NAS to send in the AA-Request packet the
      phone number that the call came from, using Automatic Number
      Identification (ANI) or similar technology. It is only used in
      AA-Request packets.

      If the Authorization-Only flag is set in the message and the
      User-Name AVP is absent, the DIAMETER Server must perform
      authorization based on this field. This can be used by a NAS to
      request whether a call should be answered based on the ANI.

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




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   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         31 for Calling-Station-Id.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         The String field is one or more octets, containing the phone
         number that the user placed the call from.

         The actual format of the information is site or application
         specific. Printable ASCII is recommended, but 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.


3.29  Proxy-State

   Description

      This Attribute is available to be sent by a proxy server to
      another server when forwarding an AA-Request and MUST be returned
      unmodified in the AA-Answer, or AA-Challenge.




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      This attribute should be removed by the proxy server before the
      response is forwarded to the NAS, and SHOULD therefore not be
      protected by the Integrity-Check-Vector or the Digital-Signature.

      A summary of the Proxy-State Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         33 for Proxy-State.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      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.


3.30  Login-LAT-Service

   Description




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      This Attribute indicates the system with which the user is to be
      connected by LAT. It MAY be used in AA-Answer packets, but only
      when LAT is specified as the Login-Service. It MAY be used in an
      AA-Request packet as a hint to the server, but the server is not
      required to honor the hint.

      Administrators use the service attribute when dealing with
      clustered systems, such as a VAX or Alpha cluster. In such an
      environment several different time sharing hosts share the same
      resources (disks, printers, etc.), and administrators often
      configure each to offer access (service) to each of the shared
      resources. In this case, each host in the cluster advertises its
      services through LAT broadcasts.

      Sophisticated users often know which service providers (machines)
      are faster and tend to use a node name when initiating a LAT
      connection. Alternately, some administrators want particular users
      to use certain machines as a primitive form of load balancing
      (although LAT knows how to do load balancing itself).

      A summary of the Login-LAT-Service Attribute format is shown
      below.  The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         34 for Login-LAT-Service.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.



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      String

         The String field is one or more octets, and contains the
         identity of the LAT service to use. The LAT Architecture allows
         this string to contain $ (dollar), - (hyphen), . (period), _
         (underscore), numerics, upper and lower case alphabetics, and
         the ISO Latin-1 character set extension [8]. All LAT string
         comparisons are case insensitive.


3.31  Login-LAT-Node

   Description

      This Attribute indicates the Node with which the user is to be
      automatically connected by LAT. It MAY be used in AA-Answer
      packets, but only when LAT is specified as the Login-Service. It
      MAY be used in an AA-Request packet as a hint to the server, but
      the server is not required to honor the hint.

      A summary of the Login-LAT-Node Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         35 for Login-LAT-Node.

      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.



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      String

         The String field is one or more octets, and contains the
         identity of the LAT Node to connect the user to. The LAT
         Architecture allows this string to contain $ (dollar), -
         (hyphen), . (period), _ (underscore), numerics, upper and lower
         case alphabetics, and the ISO Latin-1 character set extension.
         All LAT string comparisons are case insensitive.


3.32  Login-LAT-Group

   Description

      This Attribute contains a string identifying the LAT group codes
      which this user is authorized to use. It MAY be used in AA-Answer
      packets, but only when LAT is specified as the Login-Service. It
      MAY be used in an AA-Request packet as a hint to the server, but
      the server is not required to honor the hint.

      LAT supports 256 different group codes, which LAT uses as a form
      of access rights. LAT encodes the group codes as a 256 bit bitmap.

      Administrators can assign one or more of the group code bits at
      the LAT service provider; it will only accept LAT connections that
      have these group codes set in the bit map. The administrators
      assign a bitmap of authorized group codes to each user; LAT gets
      these from the operating system, and uses these in its requests to
      the service providers.

      A summary of the Login-LAT-Group Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         36 for Login-LAT-Group.



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      AVP Length

         The length of this attribute MUST be 40.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Data

         The Data field is a 32 octet bit map, most significant octet
         first. 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.


3.33  Framed-AppleTalk-Link

   Description

      This Attribute indicates the AppleTalk network number which should
      be used for the serial link to the user, which is another
      AppleTalk router. It is only used in AA-Answer packets. It is
      never used when the user is not another router.

      A summary of the Framed-AppleTalk-Link Attribute format is shown
      below. The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         37 for Framed-AppleTalk-Link.




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      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets. Despite the size of the
         field, values range from zero to 65535. The special value of
         zero indicates that this is an unnumbered serial link. A value
         of one to 65535 means that the serial line between the NAS and
         the user should be assigned that value as an AppleTalk network
         number.


3.34  Framed-AppleTalk-Network

   Description

      This Attribute indicates the AppleTalk Network number which the
      NAS should probe to allocate an AppleTalk node for the user. It is
      only used in AA-Answer packets. It is never used when the user is
      another router. Multiple instances of this Attribute indicate that
      the NAS may probe using any of the network numbers specified.

      A summary of the Framed-AppleTalk-Network Attribute format is
      shown below. The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         38 for Framed-AppleTalk-Network.



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      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets. Despite the size of the
         field, values range from zero to 65535. The special value zero
         indicates that the NAS should assign a network for the user,
         using its default cable range. A value between one and 65535
         (inclusive) indicates the AppleTalk Network the NAS should
         probe to find an address for the user.


3.35  Framed-AppleTalk-Zone

   Description

      This Attribute indicates the AppleTalk Default Zone to be used for
      this user. It is only used in AA-Answer packets. Multiple
      instances of this attribute in the same packet are not allowed.

      A summary of the Framed-AppleTalk-Zone Attribute format is shown
      below. The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         39 for Framed-AppleTalk-Zone.

      AVP Length



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         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         The name of the Default AppleTalk Zone to be used for this
         user.  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.


3.36  CHAP-Challenge

   Description

      This Attribute contains the CHAP Challenge sent by the NAS to a
      PPP Challenge-Handshake Authentication Protocol (CHAP) user. It is
      only used in AA-Request packets.

      A summary of the CHAP-Challenge Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      Type

         60 for CHAP-Challenge.

      AVP Length

         The length of this attribute MUST be at least 24.



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      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Data

         The Data field contains the CHAP Challenge.


3.37  NAS-Port-Type

   Description

      This Attribute indicates the type of the physical port of the NAS
      which is authenticating the user. It can be used instead of or in
      addition to the NAS-Port (5) attribute. It is only used in AA-
      Request packets. Either NAS-Port (5) or NAS-Port-Type or both
      SHOULD be present in an AA-Request packet, if the NAS
      differentiates among its ports.

      A summary of the NAS-Port-Type Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         61 for NAS-Port-Type.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending



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         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets. "Virtual" refers to a
         connection to the NAS via some transport protocol, instead of
         through a physical port. For example, if a user telnetted into
         a NAS to authenticate himself as an Outbound-User, the AA-
         Request might include NAS-Port-Type = Virtual as a hint to the
         RADIUS server that the user was not on a physical port.

            0       Async
            1       Sync
            2       ISDN Sync
            3       ISDN Async V.120
            4       ISDN Async V.110
            5       Virtual


3.38  Port-Limit

   Description

      This Attribute sets the maximum number of ports to be provided to
      the user by the NAS. This Attribute MAY be sent by the server to
      the client in an AA-Answer packet. It is intended for use in
      conjunction with Multilink PPP [9] or similar uses. It MAY also be
      sent by the NAS to the server as a hint that that many ports are
      desired for use, but the server is not required to honor the hint.

      A summary of the Port-Limit Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type




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         62 for Port-Limit.

      AVP Length

         The length of this attribute MUST be 12.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field is four octets, containing a 32-bit
         unsigned integer with the maximum number of ports this user
         should be allowed to connect to on the NAS.


3.39  Login-LAT-Port

   Description

      This Attribute indicates the Port with which the user is to be
      connected by LAT. It MAY be used in AA-Answer packets, but only
      when LAT is specified as the Login-Service. It MAY be used in an
      AA-Request packet as a hint to the server, but the server is not
      required to honor the hint.

      A summary of the Login-LAT-Port Attribute format is shown below.
      The fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         63 for Login-LAT-Port.




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      AVP Length

         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         The String field is one or more octets, and contains the
         identity of the LAT port to use. The LAT Architecture allows
         this string to contain $ (dollar), - (hyphen), . (period), _
         (underscore), numerics, upper and lower case alphabetics, and
         the ISO Latin-1 character set extension. All LAT string
         comparisons are case insensitive.


3.40  Filter-Rule

   Description

      This Attribute provides filter rules that need to be configured on
      the NAS for the user. It is used in the AA-Answer message and can
      appear multiple times.

      A summary of the Filter-Rule Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   String ...
      +-+-+-+-+-+-+-+-+

      Type

         280 for Filter-Rule.

      AVP Length



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         The length of this attribute MUST be at least 9.

      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      String

         The String field MUST contain a filter rule in the following
         format:  "permit (offset=value AND offset=value) OR
         offset=value" or "deny (offset=value AND offset=value) OR
         offset=value".


3.41  Framed-Password-Policy

   Description

      This Attribute is used to indicate to a peer what types of
      authentication are supported by the issuing DIAMETER peer. More
      than one Framed-Password-Policy AVP MAY be present in the Domain-
      Discovery-Answer message.

      A summary of the User-Name Attribute format is shown below. The
      fields are transmitted from left to right.

   AVP Format

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AVP Code                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          AVP Length           |     Reserved      |U|T|V|E|H|M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

         281 for Framed-Password-Policy.

      AVP Length

         The length of this attribute MUST be 12.




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      AVP Flags

         The 'M' bit MUST be set. The 'H' and 'E' MAY be set depending
         upon the security model used. The 'V', 'T' and the 'U' bits
         MUST NOT be set.

      Integer32

         The Integer32 field contains the supported authentication
         schemes supported. The following values are supported:

            PAP         1
            CHAP        2
            MS-CHAP     3
            EAP         4
            SPAP        5


3.42  Table of Attributes

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

      AA   Succ  Fail  Chal  Disc-Req Disc-Rsp #    Attribute
      Req  Answ  Answ  Req
      0-1  0-1   0     0     1        0-1       1   User-Name
      0-1  0     0     0     0        0         2   User-Password [*1]
      0-1  0     0     0     0        0         3   CHAP-Password [*1]
      0-1  0     0     0     0        0         4   NAS-IP-Address
      0-1  0     0     0     0        0         5   NAS-Port
      0-1  0-1   0     0     0        0         6   Service-Type
      0-1  0-1   0     0     0        0         7   Framed-Protocol
      0-1  0-1   0     0     0        0         8   Framed-IP-Address
      0-1  0-1   0     0     0        0         9   Framed-IP-Netmask
      0    0-1   0     0     0        0        10   Framed-Routing
      0    0+    0     0     0        0        11   Filter-Id
      0    0-1   0     0     0        0        12   Framed-MTU
      0+   0+    0     0     0        0        13   Framed-Compression
      0+   0+    0     0     0        0        14   Login-IP-Host
      0    0-1   0     0     0        0        15   Login-Service
      0    0-1   0     0     0        0        16   Login-TCP-Port
      0    0+    0+    0+    0        0        18   Reply-Message
      0-1  0-1   0     0     0        0        19   Callback-Number
      0    0-1   0     0     0        0        20   Callback-Id
      0    0+    0     0     0        0        22   Framed-Route
      0    0-1   0     0     0        0        23   Framed-IPX-Network
      0-1  0-1   0     0-1   0        0        24   State
      0    0+    0     0     0        0        25   Class



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      0    0-1   0     0-1   0-1      0-1      27   Session-Timeout
      0    0-1   0     0-1   0-1      0-1      28   Idle-Timeout
      0    0-1   0     0     0        0        29   Termination-Action
      0-1  0     0     0     0        0        30   Called-Station-Id
      0-1  0     0     0     0        0        31   Calling-Station-Id
      0-1  0     0     0     0        0        32   NAS-Identifier
      0+   0+    0+    0+    0+       0+       33   Proxy-State
      0-1  0-1   0     0     0        0        34   Login-LAT-Service
      0-1  0-1   0     0     0        0        35   Login-LAT-Node
      0-1  0-1   0     0     0        0        36   Login-LAT-Group
      0    0-1   0     0     0        0        37   Framed-AppleTalk-Link
      0    0+    0     0     0        0        38   Framed-AppleTalk-Net.
      0    0-1   0     0     0        0        39   Framed-AppleTalk-Zone
      0-1  0     0     0     0        0        60   CHAP-Challenge
      0-1  0     0     0     0        0        61   NAS-Port-Type
      0-1  0-1   0     0     0        0        62   Port-Limit
      0-1  0-1   0     0     0        0        63   Login-LAT-Port
      0    0+    0     0     0        0        280  Filter-Rule
      0    0     0     0     0+       0+       281  Framed-Password-Pol.
      AA   Succ  Fail  Chal  Disc-Req Disc-Rsp #    Attribute
      Req  Answ  Answ  Req

      [*1] An AA-Request MUST NOT contain both a User-Password and a
      CHAP-Password AVP.

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

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


4.0  Protocol Definition

   This section will outline how the DIAMETER Authentication Extension
   can be used.

4.1  Feature Advertisement/Discovery

   As defined in [2], the Reboot-Ind and Device-Feature-Query messages
   can be used to inform a peer about locally supported DIAMETER
   Extensions. In order to advertise support of this extension, the



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   Extension-Id AVP must be transmitted with a value of two (2).


4.2  Authorization Procedure

   This specification allows two different types of Authorization
   procedures.  The first method is identical to the way RADIUS works
   today and requires the AA-Request to contain the UserName as well as
   either the Password or the CHAP-Password AVPs.

   The second method is used by NASes that send AA-Request whenever they
   receive an incoming call and want to get authorization from the
   DIAMETER Server to answer the call. In this case the AA-Request
   contains the NAS-IP-Address, the Calling-Station-Id and the Called-
   Station-Id AVPs.

   In this case the DIAMETER Server can lookup the combination of the
   Calling-Station-Id and the Called-Station-Id in order to ensure that
   the pair are authorized as per the local policy.


4.3  Integration with Resource-Management

   Document [10] specifies the Resource-Token AVP that is used to carry
   information required for a DIAMETER server to rebuild its state
   information in the event of a crash or some other event that would
   cause the server to loose its state information.

   When creating the Resource-Token AVP, the following AVPs MUST be
   present, in addition to the AVPs listed in [10]; the UserName AVP,
   the NAS-IP- Address, the NAS-Port. Any additional AVP MAY be included
   if the AVP is a resource that is being managed (i.e. Framed-IP-
   Address in the case where the DIAMETER Server is allocating IP
   Addresses out of a centrally managed address pool).


4.4  RADIUS Proxies

   In today's dial up networks the RADIUS protocol is used to
   authentication, authorize and perform accounting for dial-up users.
   However, it has become common practice to make use of RADIUS Servers
   known as proxies.

   The use of proxies has become widespread especially with the
   popularity of Internet Roaming[4]. In this example a user has a
   single user account with a local service provider. When this user
   roams outside of the ISP's service area, it is possible for the user
   to connect to another service provider (see [4] for more detail).



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   In this scenario, the new service provider (ISPB) provides internet
   access for the user through a NAS (NASB). ISPB owns an authentication
   server (RADB), which proxies the authentication request to the user's
   original provider's authentication server (RADA).

                (Access-Request)           (Access-Request)
      +------+       ----->       +------+      ------>       +------+
      |      |                    |      |                    |      |
      | NASB +--------------------+ RADB +--------------------+ RADA |
      |      |                    |      |                    |      |
      +------+       <-----       +------+      <------       +------+
                 (Access-Accept)            (Access-Accept)

   The example shown above NASB generates an authentication request on
   behalf of the dial-in user to the RADB Authentication server. In this
   case, the user's identity would include a domain identifier [3] that
   would enable RADB to identify the authentication server (i.e.
   user@ISPA.com).

   The RADB server then forwards the request to RADA which authenticates
   the user based on information found within the request. If
   successfully authenticated the RADA server returns a successful
   response along with authorization information. If the user
   authentication fails RADA replies with a failed response.

   In the past this model has caused much concern over it's security
   implication.  The model is much worse in the when there exists an
   intermediate provider between ISPB and ISPA (say ISPC). The following
   diagram depicts such an example where RADB must forward any requests
   for RADA through RADC.

              (Accounting-Request)        (Accounting-Request)
      +------+       ----->       +------+      ------>       +------+
      |      |                    |      |                    |      |
      | RADB +--------------------+ RADC +--------------------+ RADA |
      |      |                    |      |                    |      |
      +------+       <-----       +------+      <------       +------+
              (Accounting-Response)       (Accounting-Response)

   The problem with the above scenario is that complete trust is placed
   in RADC (and hence ISPC) since it is very simple to modify any
   attributes found within the request or the response. The example
   shows an accounting request sent from RADB to RADA through RADC. The
   following is a list of a few attacks which can be generated by a
   malicious proxy:

      - Generating Accounting Records by replaying old
      authentication/accounting records. In this example it is very



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      simple for RADC to simple retain old packets and replay then at a
      later date. This will cause RADA to "pay" for services which were
      never rendered.

      - Modify Attributes within the request or response. In this case
      RADC can modify attributes, such as the length of the call, that
      would fool RADA into believing the call was longer than in
      reality.

      - Stealing PAP Passwords is another problem with today's proxies.
      In the current model PAP passwords are encrypted using a shared
      secret which is shared between each hop in the proxy chain. In
      this case each hop has the opportunity to decrypt, and possibly
      save for future use, the user's password.

   Given the problems identified above with the current proxy model it
   is necessary to create a mechanism which allows for non-repudiation,
   end-to-end data integrity as well as end-to-end encryption. Given the
   current encryption technology this can only be achieved with the use
   of asymetric encryption and digital signatures.


4.5  DIAMETER Proxies

   The DIAMETER protocol also makes use of proxies in order to keep the
   existing arrangements while migrating from RADIUS to DIAMETER.
   However since DIAMETER makes use of asymetric encryption and digital
   signatures it solves many of the problems shown above.

                  (AA-Request)               (AA-Request)
      +------+       ----->       +------+      ------>       +------+
      |      |                    |      |                    |      |
      | NASB +--------------------+ DIA2 +--------------------+ DIA1 |
      |      |                    |      |                    |      |
      +------+       <-----       +------+      <------       +------+
                   (AA-Answer)                (AA-Answer)

   In this example NASB generates an AA-Request that is forwarded to
   DIA2. The AA-Request contains a digital signature AVP which
   "protects" all mandatory (or non-editable) AVPs within the request.
   All AVPs which may be modified, or removed appear after the digital
   signature AVP. Once DIA2 receives the request, it MAY authenticate
   the request to ensure that it was originated by NASB (verifying the
   signature is not necessary if the link between NASB and DIA2 is
   secured using IPSEC).

   The DIA2 Server may then add new attributes to the request. All
   mandatory AVPs MUST be present prior to the non mandatory AVPs and



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   MUST be preceeded by a Digital Signature AVP (using DIA2's private
   key). Note that all non-mandatory AVPs added to the packet by NASB
   must appear after DIA2's digital signature AVP. The message is then
   forwarded towards the DIA1 server.

   Since all packets between NASB and DIA1 must flow through DIA2, it is
   not possible to use IPSEC between both hosts. Therefore DIA1 MUST
   validate NASB's digital signature AVP. However it is not necessary to
   validate DIA2's digital signature if the link between DIA2 and DIA1
   is secured using IPSEC.

   This mechanism now provides a method for DIA1 to prove that NASB was
   the initiator of the request (note that DIAMETER also includes a
   timestap to prevent replay attacks). It also provides a method of
   ensuring that DIA2 cannot modify any "non-editable" attributes (such
   as length of call, etc).

   In addition, this same mechanism can be used for end-to-end
   encryption of AVPs. In the case where NASB needs to encrypt an AVP it
   is done using asymetric encryption using DIA1's public key. This
   ensures that only DIA1 can decrypt the AVP.

   An attack has been identified in this proposal which allows a
   malicous man in the middle attack as shown in the following diagram.

             (AA-Request)      (AA-Request)      (AA-Request)
      +------+  ----->  +------+  ----->  +------+  ----->  +------+
      |      |          |      |          |      |          |      |
      | NASB +----------+ DIA2 +----------+ DIA3 +----------+ DIA1 |
      |      |          |      |          |      |          |      |
      +------+  <-----  +------+  <-----  +------+  <-----  +------+
              (AA-Answer)       (AA-Answer)       (AA-Answer)

   In this example, DIA3 traps packets generated from DIA2 towards DIA1,
   removes the AVPs added by DIA2 and inserts its own AVPs (posibly by
   trying to convince DIA1 to pay DIA3 for the services). This attack
   can be prevented by supporting a new Next-Hop AVP. In this case when
   NASB prepares a request it inserts a non-editable Next-Hop AVP which
   contains DIA2's identitity. DIA2 also adds a Next-Hop AVP with DIA1
   as the next hop.

   This mechanism ensures that a man in the middle cannot alter the
   packet by overriding the previous hop's additions and signature. DIA1
   could easily validate the packet's path with the use of the Next-Hop
   AVPs.


4.6  Domain Discovery



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   The Domain Discovery message set is very useful in determining the
   Home authentication server, the password policies for the domain, as
   a mechanism to retrieve a certificate (or a pointer to a
   certificate).

   The following example shows a case where DIA1 needs to communicate
   with DIA3. In this example it is necessary to use DIA2 as a proxy in
   order for both ISPs to communicate. Although this MAY be desireable
   in some business models, there are cases where it is beneficial to
   remove the proxy altogether and allow both DIA3 and DIA1 to
   communicate in a secure fashion.

                  (DD-Request)               (DD-Request)
      +------+       ----->       +------+      ------>       +------+
      |      |                    |      |                    |      |
      | DIA1 +--------------------+ DIA2 +--------------------+ DIA3 |
      |      |                    |      |                    |      |
      +------+       <-----       +------+      <------       +------+
                  (DD-Response)              (DD-Response)

   The way the Domain Discovery works is that prior to sending out an
   authentication request DIA1 would issue a Domain Discovery message
   towards DIA2. This message is protected with the digital signature as
   well as the Next-Hop AVP. DIA2 would then forward the request to DIA3
   including the Next-Hop and the digital signature AVP.

   When DIA3 receives the request, it MUST save the certificate (or the
   pointer to the certificate) and respond back including the local
   password policy, DIA3's certificate, it's contact information (i.e.
   IP address) and protect the response with the digital signature.

   Note that in all cases the TimeStamp AVP is also present to ensure no
   reply packets are accepted.

   When DIA2 receives the packet, it must add the Next-Hop AVP as well
   as the digital signature AVP. When DIA1 receives the packet it then
   knows a direct route to communicate with DIA3 since the contact
   information is present in the response. The fact that both DIA1 and
   DIA3 can now communicate directly allows both peers to use IPSEC to
   protect the message exchange (note that it MAY be desirable to also
   use the digital signature in order to keep the information in the
   DIAMETER logs).

                                       (AA-Request)
                     +------+       ----->       +------+
                     |      |                    |      |
                     | DIA1 +--------------------+ DIA3 |
                     |      |                    |      |



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                     +------+       <-----       +------+
                                        (AA-Answer)

     In addition, the password policy is also present which can indicate
     whether DIA3 is willing to accept CHAP, PAP or EAP authentication.

     Note that the Domain-Discovery-Request/Answer MAY include the
     Supported-Extension AVPs [2].


5.0  References

    [1] Rigney, et alia, "RADIUS", RFC-2138, Livingston, April 1997

    [2] Calhoun, Rubens, "DIAMETER Base Protocol", Internet-Draft,
        draft-calhoun-diameter-03.txt, May 1998.

    [3] Aboba, Beadles, "Network Address Identifier", Internet-
        Draft, draft-ietf-roamops-nai-10.txt, February 1998.

    [4] Aboba, Zorn, "Dialup Roaming Requirements", Internet-Draft,
        July 1997.

    [5] Calhoun, Rubens, Aboba, "DIAMETER Extensible Authentication
        Protocol Extensions", Internet-Draft, draft-calhoun-
        diameter-eap-01.txt, March 1998.

    [6] Calhoun, Haag, Zorn, "EAP Authentication for SOCKS
        Version 5", draft-ietf-aft-socks-eap-00.txt, March 1998.

    [7] Jacobson, "Compressing TCP/IP headers for low-speed serial
        links", RFC 1144, February 1990.

    [8] ISO 8859. International Standard -- Information Processing --
        8-bit Single-Byte Coded Graphic Character Sets -- Part 1: Latin
        Alphabet No. 1, ISO 8859-1:1987.
        <URL:http://www.iso.ch/cate/d16338.html>

    [9] Sklower, Lloyd, McGregor, Carr, "The PPP Multilink Protocol
        (MP)", RFC 1717, November 1994.

    [10] Calhoun, Greene, "DIAMETER Resource Management Extension",
         Internet-Draft, draft-calhoun-diameter-res-mgmt-01.txt,
         May 1998.

    [11] Calhoun, Zorn, Pan, "DIAMETER Framework", Internet-
         Draft, draft-calhoun-diameter-framework-00.txt, May 1998




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INTERNET DRAFT                                                 July 1998


6.0  Acknowledgements

   The Author wishes to thank Carl Rigney since much of the text in the
   document was shamefully copied from [1] as well as the following
   people for their help in the development of this protocol:

   Nancy Greene, Ryan Moats


7.0  Authors' Addresses

   Questions about this memo can be directed to:

      Pat R. Calhoun
      Technology Development
      Sun Microsystems, Inc.
      15 Network Circle
      Menlo Park, California, 94025
      USA

       Phone:  1-650-786-7733
         Fax:  1-650-786-6445
      E-mail:  pcalhoun@eng.sun.com

      William Bulley
      Merit Network, Inc.
      4251 Plymouth Road, Suite C
      Ann Arbor, Michigan, 48105-2785
      USA

       Phone:  1-734-764-9993
         Fax:  1-734-647-3185
      E-mail:  web@merit.edu


















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