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INTERNET DRAFT                                            Pat R. Calhoun
Category: Standards Track                         Sun Microsystems, Inc.
Title: draft-calhoun-diameter-nasreq-05.txt               William Bulley
Date: September 2000                                 Merit Network, Inc.
                                                         Allan C. Rubens
                                                       Tut Systems, Inc.
                                                               Jeff Haag
                                                           Cisco Systems



                       DIAMETER NASREQ Extensions



Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  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."

   The list of current Internet-Drafts can be accessed at:

      http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at:

      http://www.ietf.org/shadow.html.

   This document is an individual contribution for consideration by the
   AAA Working Group of the Internet Engineering Task Force.  Comments
   should be submitted to the diameter@diameter.org mailing list.

   Distribution of this memo is unlimited.

   Copyright   (C) The Internet Society 1999.  All Rights Reserved.








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Abstract

   This document describes the DIAMETER extension that is used for AAA
   in a PPP/SLIP Dial-Up and Terminal Server Access environment.  This
   extension, combined with the base protocol, satisfies the
   requirements defined in the NASREQ AAA criteria specification and the
   ROAMOPS AAA Criteria specification.

   Given that it is expected that initial deployments of the DIAMETER
   protocol in a dial-up environment will include legacy systems, this
   extension was carefully designed to ease the burden of servers that
   must perform protocol conversion between RADIUS and DIAMETER.  This
   is achieved by re-using the RADIUS address space, eliminating the
   need to perform attribute lookups.


Table of Contents

      1.0  Introduction
            1.1  Requirements language
      2.0  Supported AVPs
            2.1  DIAMETER AVPs
                  2.1.1  Request-Type AVP
                  2.1.2  Filter-Rule AVP
            2.2  Legacy RADIUS Attributes
                  2.2.1  NAS-IP-Address AVP
                  2.2.2  NAS-Identifier AVP
                  2.2.3  State AVP
                  2.2.4  Class AVP
      3.0  Legacy PPP Authentication Support
            3.1  Command-Codes Values
                  3.1.1  AA-Request (AAR) Command
                        3.1.1.1  User-Password AVP
                        3.1.1.2  CHAP-Password AVP
                        3.1.1.3  CHAP-Challenge AVP
                  3.1.2  AA-Answer (AAA) Command
                  3.1.3  AA-Challenge-Ind (ACI) Command
            3.2  Reply-Message AVP
      4.0  Extensible Authentication Protocol Support
            4.1  Alternative Uses
            4.2  Command-Codes Values
                  4.2.1  DIAMETER-EAP-Request (DER) Command
                  4.2.2  DIAMETER-EAP-Answer (DEA) Command
                  4.2.3  DIAMETER-EAP-Ind (DEI) Command
            4.3  EAP-Payload AVP
      5.0  DIAMETER Session Termination
      6.0  Legacy Authorization AVPs
            6.1  Service Identification AVPs



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                  6.1.1  NAS-Port AVP
                  6.1.2  Service-Type AVP
                  6.1.3  Filter-Id AVP
                  6.1.4  Callback-Number AVP
                  6.1.5  Callback-Id AVP
                  6.1.6  Idle-Timeout AVP
                  6.1.7  Called-Station-Id AVP
                  6.1.8  Calling-Station-Id AVP
                  6.1.9  NAS-Port-Type AVP
                  6.1.10 Port-Limit AVP
                  6.1.11 Filter-Rule AVP
            6.2  Framed Access Authorization AVPs
                  6.2.1  Framed-Protocol AVP
                  6.2.2  Framed-IP-Address AVP
                  6.2.3  Framed-IP-Netmask AVP
                  6.2.4  Framed-Routing AVP
                  6.2.5  Framed-MTU AVP
                  6.2.6  Framed-Compression AVP
                  6.2.7  Framed-IP-Route AVP
                  6.2.8  Framed-IPX-Network AVP
                  6.2.9  Framed-AppleTalk-Link AVP
                  6.2.10 Framed-AppleTalk-Network AVP
                  6.2.11 Framed-AppleTalk-Zone AVP
            6.3  Non-Framed Access Authorization AVPs
                  6.3.1  Login-IP-Host AVP
                  6.3.2  Login-Service AVP
                  6.3.3  Login-TCP-Port AVP
                  6.3.4  Login-LAT-Service AVP
                  6.3.5  Login-LAT-Node AVP
                  6.3.6  Login-LAT-Group AVP
                  6.3.7  Login-LAT-Port AVP
            6.4  Tunneling AVPs
                  6.4.1  Tunnel-Type AVP
                  6.4.2  Tunnel-Medium-Type AVP
                  6.4.3  Tunnel-Client-Endpoint AVP
                  6.4.4  Tunnel-Server-Endpoint AVP
                  6.4.5  Tunnel-Password AVP
                  6.4.6  Tunnel-Private-Group-ID AVP
                  6.4.7  Tunnel-Assignment-ID AVP
                  6.4.8  Tunnel-Preference AVP
                  6.4.9  Tunnel-Client-Auth-ID AVP
                  6.4.10 Tunnel-Server-Auth-ID AVP
      7.0  Interactions with Resource Management
      8.0  IANA Considerations
            8.1  Request-Type AVP Values
      9.0  Security Considerations
      10.0  References
      11.0  Acknowledgements



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      12.0 Authors' Addresses
      13.0 Full Copyright Statement


1.0  Introduction

   This document describes the DIAMETER extension that is used for AAA
   in a PPP/SLIP Dial-Up and Terminal Server Access environment.  This
   extension, combined with the base protocol [2], satisfies the
   requirements defined in the NASREQ AAA criteria specification [24]
   and the ROAMOPS AAA Criteria specification [4].

   This document is divided into three main sections. The first section
   defines the DIAMETER Command-Codes and AVPs that are needed to
   support legacy PPP authentication protocols, those that are typically
   supported by RADIUS [1] servers. The second section defines the
   Command-Codes and AVPs necessary for a DIAMETER node to support PPP's
   Extensible Authentication Protocol (EAP) [25].  The third section
   contains the Authorization AVPs that are needed for the various
   services offered by a NAS, such as PPP dial-in, terminal server and
   tunneling applications, such as L2TP [16].

   Given that it is expected that initial deployments of the DIAMETER
   protocol in a dial-up environment will include legacy systems, this
   extension was carefully designed to ease the burden of servers that
   must perform protocol conversion between RADIUS and DIAMETER.  This
   is achieved by re-using the RADIUS address space, eliminating the
   need to perform attribute lookups.

   The value assigned for the Extension-Id [2] AVP is one (1).


1.1  Requirements language

   In this document, the key words "MAY", "MUST, "MUST NOT", "optional",
   "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as
   described in [12].


2.0  Supported AVPs

   This section lists all of the DIAMETER AVPs and the legacy RADIUS
   attributes supported by this extension.


2.1  DIAMETER AVPs

   This section will define all of the AVPs that are not backward



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   compatible with the RADIUS protocol [1]. A DIAMETER message that
   includes one of these AVPs MAY cause interoperability issues should
   the request traverse a AAA node that only supports the RADIUS
   protocol. However, the DIAMETER protocol SHOULD NOT be hampered from
   future developments due to the existing installed base.

   The following table describes the DIAMETER AVPs defined in the NASREQ
   extension, their AVP Code values, types, possible flag values and
   whether the AVP MAY be encrypted.

                                            +---------------------+
                                            |    AVP Flag rules   |
                                            |----+-----+----+-----|----+
                    AVP   Section  Value    |    |     |SHLD| MUST|MAY |
   Attribute Name   Code  Defined  Type     |MUST| MAY | NOT|  NOT|Encr|
   -----------------------------------------|----+-----+----+-----|----+
   Filter-Rule      400   2.1.2    String   | M  |  P  |    |  V  | Y  |
   Request-Type     401   2.1.1    Integer32| M  |  P  |    |  V  | N  |
   EAP-Payload      402   4.2      Data     | M  |  P  |    |  V  | Y  |


2.1.1  Request-Type AVP

   The Request-Type AVP (AVP Code 401) is of type Integer32 and is used
   to determine the type of request being transmitted. Note that a
   request with this AVP set to a value other than
   AUTHORIZE_AUTHENTICATE MAY break backward RADIUS compatibility. The
   following values are defined:

      AUTHENTICATE_ONLY          1
         The request being sent is for authentication only, and MUST
         contain the relevant authentication AVPs that are needed by the
         DIAMETER server to authenticate the user.

      AUTHORIZE_ONLY             2
         The request being sent is for authorization only, and MUST
         contain the authorization AVPs that are necessary to identify
         the service being requested/offered.

      AUTHORIZE_AUTHENTICATE     3
         The request contains a request for both authentication and
         authorization. The request MUST include both the relevant
         authentication information, and authorization information
         necessary to identify the service being requested/offered.


2.1.2  Filter-Rule AVP




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   The Filter-Rule AVP (AVP Code 400) is of type String and provides
   filter rules that need to be configured on the NAS for the user. One
   or more such AVPs MAY be present in an authorization response.

   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". The keyword
   "permit" means that the filter will allow any traffic that matches
   the rule, while deny will not allow the traffic to be routed. The
   filter rules can also use the keywords "AND" and "OR", for which no
   additional explanation is necessary. The braces "(" and ")" can be
   used to setup grouping of expressions.


2.2  Legacy RADIUS Attributes

   The DIAMETER protocol reserves the first 255 AVP identifiers for
   "legacy RADIUS" support, and SHOULD only used when a DIAMETER/RADIUS
   gateway function is invoked. The following table contains the RADIUS
   attributes supported by this DIAMETER extension, their AVP code
   values, types, possible flag values and whether the AVP MAY be
   encrypted.

                                            +---------------------+
                                            |    AVP Flag rules   |
                                            |----+-----+----+-----|----+
                    AVP   Section  Value    |    |     |SHLD| MUST|MAY |
   Attribute Name   Code  Defined  Type     |MUST| MAY | NOT|  NOT|Encr|
   -----------------------------------------|----+-----+----+-----|----+
   User-Password      2   3.1.1.1  Data     | M  |  P  |    |  V  | Y  |
   CHAP-Password      3   3.1.1.2  Data     | M  |  P  |    |  V  | Y  |
   NAS-IP-Address     4   2.2.1    Address  | M  |  P  |    |  V  | Y  |
   NAS-Port           5   6.1.1    Integer32| M  |  P  |    |  V  | Y  |
   Service-Type       6   6.1.2    Integer32| M  |  P  |    |  V  | Y  |
   Framed-Protocol    7   6.2.1    Integer32| M  |  P  |    |  V  | Y  |
   Framed-IP-Address  8   6.2.2    Address  | M  |  P  |    |  V  | Y  |
   Framed-IP-Netmask  9   6.2.3    Address  | M  |  P  |    |  V  | Y  |
   Framed-Routing    10   6.2.4    Integer32| M  |  P  |    |  V  | Y  |
   Filter-Id         11   6.1.3    String   | M  |  P  |    |  V  | Y  |
   Framed-MTU        12   6.2.5    Integer32| M  |  P  |    |  V  | Y  |
   Framed-           13   6.2.6    Integer32| M  |  P  |    |  V  | Y  |
     Compression                            |    |     |    |     |    |
   Login-IP-Host     14   6.3.1    Address  | M  |  P  |    |  V  | Y  |
   Login-Service     15   6.3.2    Integer32| M  |  P  |    |  V  | Y  |
   Login-TCP-Port    16   6.3.3    Integer32| M  |  P  |    |  V  | Y  |
   Reply-Message     18   3.2      String   | M  |  P  |    |  V  | Y  |
   Callback-Number   19   6.1.4    String   | M  |  P  |    |  V  | Y  |
   Callback-Id       20   6.1.5    String   | M  |  P  |    |  V  | Y  |



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   Framed-IP-Route   22   6.2.7    String   | M  |  P  |    |  V  | Y  |
   Framed-IPX-Route  23   6.2.8    String   | M  |  P  |    |  V  | Y  |
   State             24   2.2.3    Data     | M  |  P  |    |  V  | Y  |
   Class             25   2.2.4    Data     | M  |  P  |    |  V  | Y  |
   Idle-Timeout      28   6.1.6    Integer32| M  |  P  |    |  V  | Y  |
   Called-Station-Id 30   6.1.7    String   | M  |  P  |    |  V  | Y  |
   Calling-Station-  31   6.1.8    String   | M  |  P  |    |  V  | Y  |
     Id                                     |    |     |    |     |    |
   NAS-Identifier    32   2.2.2    String   | M  |  P  |    |  V  | Y  |
   Login-LAT-Service 34   6.3.4    Integer32| M  |  P  |    |  V  | Y  |
   Login-LAT-Node    35   6.3.5    String   | M  |  P  |    |  V  | Y  |
   Login-LAT-Group   36   6.3.6    Data     | M  |  P  |    |  V  | Y  |
   Framed-Appletalk- 37   6.2.9    Integer32| M  |  P  |    |  V  | Y  |
     Link                                   |    |     |    |     |    |
   Framed-Appletalk- 38   6.2.10   Integer32| M  |  P  |    |  V  | Y  |
     Network                                |    |     |    |     |    |
   Framed-Appletalk- 39   6.2.11   Data     | M  |  P  |    |  V  | Y  |
     Zone                                   |    |     |    |     |    |
   CHAP-Challenge    60   3.1.1.3  Data     | M  |  P  |    |  V  | Y  |
   NAS-Port-Type     61   6.1.9    Integer32| M  |  P  |    |  V  | Y  |
   Port-Limit        62   6.1.10   Integer32| M  |  P  |    |  V  | Y  |
   Login-LAT-Port    63   6.3.7    String   | M  |  P  |    |  V  | Y  |
   Tunnel-Type       64   6.4.1    Integer32| M  |  P  |    |  V  | Y  |
   Tunnel-Medium-    65   6.4.2    Integer32| M  |  P  |    |  V  | Y  |
     Type                                   |    |     |    |     |    |
   Tunnel-Client-    66   6.4.3    String   | M  |  P  |    |  V  | Y  |
     Endpoint                               |    |     |    |     |    |
   Tunnel-Server-    67   6.4.4    String   | M  |  P  |    |  V  | Y  |
     Endpoint                               |    |     |    |     |    |
   Tunnel-Password   69   6.4.5    String   | M  |  P  |    |  V  | Y  |
   Tunnel-Private-   81   6.4.6    String   | M  |  P  |    |  V  | Y  |
     Group-ID                               |    |     |    |     |    |
   Tunnel-           82   6.4.7    String   | M  |  P  |    |  V  | Y  |
     Assignment-Id                          |    |     |    |     |    |
   Tunnel-Preference 83   6.4.8    Integer32| M  |  P  |    |  V  | Y  |
   Tunnel-Client-    90   6.4.9    String   | M  |  P  |    |  V  | Y  |
     Auth-ID                                |    |     |    |     |    |
   Tunnel-Server-    91   6.4.10   String   | M  |  P  |    |  V  | Y  |
     Auth-ID                                |    |     |    |     |    |


2.2.1  NAS-IP-Address AVP

   The Host-IP-Address AVP (AVP Code 4) [1] is of type Address, and
   contains the IP Address of the NAS providing service to the user.
   When this AVP is present, the Host-Name AVP DOES NOT represent the
   NAS providing service to the user. Note that this AVP SHOULD only
   added by a RADIUS/DIAMETER protocol gateway [28].



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2.2.2  NAS-Identifier AVP

   The NAS-Identifier AVP (AVP Code 32) [1] is of type String, and
   contains the Identity of the NAS providing service to the user.  When
   this AVP is present, the Host-Name AVP DOES NOT represent the NAS
   providing service to the user. Note that this AVP SHOULD only added
   by a RADIUS/DIAMETER protocol gateway [28].


2.2.3  State AVP

   The State AVP (AVP Code 24) is used to transmit the contents of the
   RADIUS State attribute, and no interpretation of the contents should
   be made.  Note that this AVP SHOULD only added by a RADIUS/DIAMETER
   protocol gateway [28].


2.2.4  Class AVP

   The Class AVP (AVP Code 25) is used to transmit the contents of the
   RADIUS Class attribute, and no interpretation of the contents should
   be made.  Note that this AVP SHOULD only added by a RADIUS/DIAMETER
   protocol gateway [28].


3.0  Legacy PPP Authentication Support

   This section defines the new Command-Code [2] values required to
   support the legacy PPP authentication protocol (PAP, CHAP), as well
   as the AVPs that are necessary to carry the authentication
   information in the DIAMETER protocol. The functionality defined here
   provides a RADIUS-like AAA service, over a more reliable and secure
   transport, as defined in the base protocol [2].

   Unlike the RADIUS protocol [1], the DIAMETER protocol does not
   require authentication information to be contained in a request from
   the client. Therefore, it is possible to send a request for
   authorization only. The type of service depends upon the Request-Type
   AVP. This difference MAY cause operational issues in environments
   that need RADIUS interoperability, and it MAY be necessary that
   protocol conversion gateways add some authentication information when
   transmitting to a RADIUS server.


3.1  Command-Codes Values

   This section defines new Command-Code [2] values that MUST be
   supported by all DIAMETER implementations that conform to this



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   specification. The following Command Codes are defined in this
   section:

      Command-Name             Abbrev.    Code       Reference
      --------------------------------------------------------
      AA-Request                AAR       265          3.1.1
      AA-Answer                 AAA       266          3.1.2
      AA-Challenge-Ind          ACI       267          3.1.3


3.1.1  AA-Request (AAR) Command

   The AA-Request message (AAR), indicated by the Command-Code field set
   to 265, is used in order to request authentication and/or
   authorization for a given PPP user. The type of request is identified
   through the Request-Type AVP, and the default mode is both
   authentication and authorization.

   If Authentication is requested the User-Name attribute SHOULD be
   present, as well as any additional authentication AVPs that would
   carry the password information. A request for authorization only
   SHOULD include the information from which the authorization will be
   performed, such as the DNIS and ANI AVPs. Certain networks MAY use
   different AVPs for authorization purposes. A request for
   authorization will include some AVPs defined in sections 2.0 and 6.0.

   It is possible for a single session to be authorized only first, then
   followed by an authentication request. However, the inverse SHOULD
   NOT be permitted.

   If the AA-Request is a result of an AA-Challenge-Ind, the Session-Id
   MUST be identical as the one provided in the initial AA-Request for
   the same session. If the AA-Request is a result of an AA-Challenge-
   Ind that included a State AVP, the same AVP MUST be present in the
   following AA-Request.


   Message Format













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      <AA-Request> ::= <DIAMETER Header, Command-Code = 265>
                       <Session-Id AVP>
                       <Host-Name AVP>
                       [<Destination-NAI>]
                       [<NAS-IP-Address>]
                       [<NAS-Identifier>]
                       [<User-Name AVP>]
                       [<User-Password AVP> ||
                        <CHAP-Password AVP> &&
                        <CHAP-Challenge AVP>]
                       [<State AVP>]
                       [<Authorization AVPs>]
                       [<Timestamp AVP>
                        <Nonce AVP>
                        <Integrity-Check-Vector AVP>]


3.1.1.1  User-Password AVP

   The User-Password AVP (AVP Code 2) is of type Data and contains the
   password of the user to be authenticated, or the user's input
   following an AA-Challenge-Ind.

   This AVP MUST be encrypted using one of the methods described in [2]
   or [13]. Unless this AVP is used for one-time passwords, the User-
   Password AVP SHOULD NOT be used in non-trusted proxy environments.

   The clear-text password (prior to encryption) MUST NOT be longer than
   128 bytes in length.


3.1.1.2  CHAP-Password AVP

   The CHAP-Password AVP (AVP Code 3) is of type Complex and contains
   the response value provided by a PPP Challenge-Handshake
   Authentication Protocol (CHAP) [6] user in response to the challenge.

   If the CHAP-Password AVP is found in a message, the CHAP-Challenge
   AVP (see section 3.1.1.3) MUST be present as well.

      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 Header (AVP Code = 3)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  CHAP Ident   |    Data ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   The CHAP Ident field contains the one octet CHAP Identifier from the
   user's CHAP response [6]. The Data field is 16 octets, and contains
   the CHAP Response from the user. The actual computation of the CHAP
   response can be found in [6].


3.1.1.3  CHAP-Challenge AVP

   The CHAP-Challenge AVP (AVP Code 60) is of type Data and contains the
   CHAP Challenge sent by the NAS to a PPP Challenge-Handshake
   Authentication Protocol (CHAP) [6] user.


3.1.2  AA-Answer (AAA) Command

   The AA-Answer (AAA) message, indicated by the Command-Code field set
   to 266, is sent in response to the AA-Request message. If
   authorization was requested, a successful response will include the
   authorization AVPs appropriate for the service being provided, as
   defined in section 2.0 and 6.0.

   Message Format

      <AA-Answer> ::= <DIAMETER Header, Command-Code = 266>
                       <Session-Id AVP>
                       <Result-Code AVP>
                       <Host-Name AVP>
                       <Destination-NAI>
                       [<User-Name AVP>]
                       [<Authorization AVPs>]
                       [<Timestamp AVP>
                        <Nonce AVP>
                        <Integrity-Check-Vector AVP>]


3.1.3  AA-Challenge-Ind (ACI) Command

   The AA-Challenge-Ind (ACI) message, indicated by the Command-Code
   field set to 267, is sent by a DIAMETER Home server to issue a
   challenge requiring a response to a dial-up user. The message MAY
   have one or more Reply-Message AVP, the User-Name AVP and it MAY have
   zero or one State AVP. No other AVPs are permitted in an AA-
   Challenge-Ind other than security related AVPs [2, 13].

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

   A NAS that supports PAP MAY forward the Reply-Message to the dial-in
   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.

   When possible, authentication mechanisms that include more than a
   single authentication round trip SHOULD use EAP (see section 4.0)
   instead of the AA-Challenge-Ind. This command has been maintained for
   RADIUS backward compatibility.

      AA-Challenge-Ind ::= <DIAMETER Header, Command-Code = 267>
                           <Session-Id AVP>
                           <Result-Code AVP>
                           <Host-Name AVP>
                           <Destination-NAI>
                           [<User-Name AVP>]
                           [<State AVP>]
                           [<Reply-Message AVPs>]
                           [<Timestamp AVP>
                            <Nonce AVP>
                            <Integrity-Check-Vector AVP>]


3.2  Reply-Message AVP

   The Reply-Message AVP (AVP Code 18) is of type String and contains
   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.

   The Reply-Message AVP MAY indicate a dialog message to prompt the
   user before another AA-Request attempt. When used in an AA-
   Challenge-Ind, 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
   message.





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4.0  Extensible Authentication Protocol Support

   The Extensible Authentication Protocol (EAP), described in [25],
   provides a standard mechanism for support of additional
   authentication methods within PPP. Through the use of EAP, support
   for a number of authentication schemes may be added, including smart
   and token cards, Kerberos, Public Key, One Time Passwords, and
   others.

   This section describes the Command-Codes values and AVPs that are
   required for an EAP payload to be encapsulated within the DIAMETER
   protocol. Since authentication occurs between the PPP client and its
   home DIAMETER server, end-to-end authentication is achieved, reducing
   the possibility for fraudulent authentication, such as replay and
   man-in-the-middle attacks. End-to-end authentication also provides
   for mutual (bi-directional) authentication, which is not possible
   with PAP and CHAP in a roaming environment.

   The DIAMETER/EAP extension allows a home DIAMETER server to initiate
   an unsolicited authentication request to the user. This allows the
   home server to periodically ensure that the user is still active,
   which is useful when a server requires re-authentication to extend
   the "life" of a session [26]. Server-initiated authentication can
   reduce the number of protocol exchanges over the Internet.

   The EAP conversation between the authenticating peer and the NAS
   begins with the negotiation of EAP within LCP. Once EAP has been
   negotiated, the NAS will typically send to the DIAMETER server a
   DIAMETER-EAP-Request message with a NULL EAP-Payload AVP, signifying
   an EAP-Start. The Port number and NAS Identifier MUST be included in
   the AVPs issued by the NAS in the DIAMETER-EAP-Request packet.

   If the DIAMETER home server supports EAP, it MUST respond with a
   DIAMETER-EAP-Ind message containing an EAP-Payload AVP that includes
   an encapsulated EAP payload [25]. The EAP payload is forwarded by the
   NAS to the PPP client. The initial DIAMETER-EAP-Ind normally includes
   an EAP-Request/Identity, requesting the PPP client to identify
   itself. Upon receipt of the PPP client's EAP-Response [25], the NAS
   will then issue a second DIAMETER-EAP-Request message, with the
   client's EAP payload encapsulated within the EAP-Payload AVP. The
   conversation continues until the DIAMETER server sends a DIAMETER-
   EAP-Answer with a Result-Code AVP indicating success or failure. A
   Result-Code AVP containing a failure indication SHOULD also include
   an EAP-Payload AVP containing an EAP-Failure [25] payload, and the
   NAS SHOULD disconnect the PPP client by issuing a LCP terminate. If
   the Result-Code AVP indicates success, the EAP-Payload AVP MUST
   encapsulate an EAP-Success [25] payload, and the NAS SHOULD
   successfully terminate the PPP authentication phase. If authorization



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   was requested, a successful DIAMETER-EAP-Answer MUST also include the
   appropriate authorization AVPs required for the service requested
   (see sections 2.0 and 6.0).

   The above scenario creates a situation in which the NAS never needs
   to manipulate an EAP packet. An alternative may be used in situations
   where an EAP-Request/Identity message will always be sent by the NAS
   to the authenticating peer. This involves having the NAS send an
   EAP-Request/Identity message to the PPP client, and forwarding the
   EAP-Response/Identity packet to the DIAMETER server in the EAP-
   Payload AVP of a DIAMETER-EAP-Request packet. While this approach
   will save a round-trip, it cannot be universally employed. There are
   circumstances in which the user's identity may not be needed (such as
   when authentication and accounting is handled based on the calling or
   called phone number), and therefore an EAP-Request/Identity packet
   may not necessarily be issued by the NAS to the authenticating peer.

   Unless the NAS interprets the EAP-Response/Identity packet returned
   by the authenticating peer, it will not have access to the user's
   identity. Therefore, the DIAMETER Server SHOULD return the user's
   identity by inserting it in the User-Name attribute of subsequent
   DIAMETER-EAP-Answer packets. Without the user's identity, the
   Session-Id AVP MAY be used for accounting and billing, however
   operationally this MAY be very difficult to manage.

   The DIAMETER-EAP-Ind message MAY be sent by a DIAMETER server in
   order to initiate an unsolicited authentication of the PPP user, as
   described in [26]. This functionality allows a home DIAMETER server
   to easily extend the "life" of a session for a particular service,
   while reducing the total number of authentication round-trips, should
   the NAS initiate the periodic authentication.

   Should an EAP authentication session be interrupted due to a home
   server failure, the session MAY be directed to an alternate server,
   but the authentication session will have to be restarted from the
   beginning.

   When DIAMETER is used in a roaming environment, the NAS SHOULD issue
   the EAP-Request/Identity request to the PPP client, and forward the
   EAP-Response in the initial DIAMETER-EAP-Request message. This allows
   any DIAMETER proxies or brokers to identify the user, and forward the
   message to the appropriate home server. If a response is received
   with the Result-Code set to DIAMETER_COMMAND_UNSUPPORTED [2], it is
   an indication that a DIAMETER server in the proxy chain does not
   support EAP. The NAS MAY re-open LCP and attempt to negotiate another
   PPP authentication protocol, such as PAP or CHAP. A NAS SHOULD be
   cautious when determining whether a less secure authentication
   protocol will be used, since this could be a result of a bidding down



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   attack. See [28] for additional information.


4.1  Alternative uses

   Currently the conversation between the backend authentication server
   and the DIAMETER server is proprietary because of lack of
   standardization. In order to increase standardization and provide
   interoperability between DIAMETER vendors and backend security
   vendors, it is recommended that DIAMETER-encapsulated EAP be used for
   this conversation.

   This has the advantage of allowing the DIAMETER server to support EAP
   without the need for authentication-specific code within the DIAMETER
   server. Authentication-specific code can then reside on a backend
   authentication server instead.

   In the case where DIAMETER-encapsulated EAP is used in a conversation
   between a DIAMETER server and a backend authentication server, the
   latter will typically return an DIAMETER-EAP-Answer/EAP-Payload/EAP-
   Success message without inclusion of the expected authorization AVPs
   required in a successful response. This means that the DIAMETER
   server MUST add these attributes prior to sending an DIAMETER-EAP-
   Answer/EAP-Payload/EAP-Success message to the NAS.


4.2  Command-Codes Values

   This section defines new Command-Code [2] values that MUST be
   supported by all DIAMETER implementations conforming to this
   specification. The following Command Codes are defined in this
   section:

      Command-Name             Abbrev.    Code       Reference
      --------------------------------------------------------
      DIAMETER-EAP-Request      DER       268          4.2.1
      DIAMETER-EAP-Answer       DEA       269          4.2.2
      DIAMETER-EAP-Ind          DEI       270          4.2.3
      DIAMETER-EAP-Terminate    DET       275          4.2.4



4.2.1  DIAMETER-EAP-Request (DER) Command

   The DIAMETER-EAP-Request (DER) command, indicated by the Command-Code
   field set to 268, is sent by a DIAMETER client to a DIAMETER server
   and conveys an EAP-Response [25] from the dial-up PPP client. The
   DIAMETER-EAP-Request MUST contain one EAP-Payload AVP, which contains



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   the actual EAP payload. An EAP-Payload AVP with no data MAY be sent
   to the DIAMETER server to initiate an EAP authentication session.

   Upon receipt of a DIAMETER-EAP-Request, a DIAMETER server MUST issue
   a reply. The reply may be either:

      1) a DIAMETER-EAP-Ind containing an EAP-Request encapsulated
         within an EAP-Payload attribute
      2) a DIAMETER-EAP-Answer containing an EAP-Success encapsulated
         within an EAP-Payload and a Result-Code indicating success.
      3) a DIAMETER-EAP-Answer containing an EAP-Failure encapsulated
         within an EAP-Payload and a Result-Code indicating failure.
      4) A Message-Reject-Ind packet with a Result-Code set to
         DIAMETER_COMMAND_UNSUPPORTED if a DIAMETER server does not
         support the EAP extension.

   Message Format

      <DIAMETER-EAP-Request> ::= <DIAMETER Header, Command-Code = 268>
                                 <Host-Name AVP>
                                 [<Destination-NAI>]
                                 [<NAS-IP-Address>]
                                 [<NAS-Identifier>]
                                 <EAP-Payload AVP>
                                 <User-Name AVP>
                                 [<Timestamp AVP>
                                  <Initialization-Vector AVP>
                                  <Integrity-Check-Vector AVP>]


4.2.2  DIAMETER-EAP-Answer (DEA) Command

   The DIAMETER-EAP-Answer (DEA) message, indicated by the Command-Code
   field set to 269, is sent by the DIAMETER server to the client to
   indicate either a successful or failed authentication. The DIAMETER-
   EAP-Answer message SHOULD include an EAP payload of type EAP-Success
   or EAP-Failure encapsulated within an EAP-Payload AVP. The Result-
   Code AVP MUST indicate a failure if the EAP-Failure payload is
   present, while the AVP MUST indicate success if the EAP-Success
   payload is present.

   If the message from the DIAMETER client included a request for
   authorization, a successful response MUST include the authorization
   AVPs that are relevant to the service being provided.

   Message Format

      <DIAMETER-EAP-Answer> ::= <DIAMETER Header, Command-Code = 269>



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                                <Result-Code AVP>
                                <Host-Name AVP>
                                <Destination-NAI>
                                [<User-Name AVP>]
                                [<EAP-Payload AVP>]
                                [<Authorization AVPs>]
                                [<Timestamp AVP>
                                 <Initialization-Vector AVP>
                                 <Integrity-Check-Vector AVP>]


4.2.3  DIAMETER-EAP-Ind (DEI) Command

   The DIAMETER-EAP-Ind (DEI) command, indicated by the Command-Code set
   to 270, has two uses. This message MAY be sent in response to a
   DIAMETER-EAP-Request message, and MUST contain an EAP-Response
   payload [25] encapsulated within an EAP-Payload AVP.

   Alternatively, this message MAY also be sent unsolicited from a
   DIAMETER server to a client to request re-authentication of a PPP
   client. For re-authentication, it is recommended that the Identity
   request be skipped in order to reduce the number of authentication
   round trips. This is only possible when the user's identity is
   already known by the home DIAMETER server.

   Upon receipt of the message, the NAS MUST issue the EAP payload to
   the PPP Client, and SHOULD respond with a DIAMETER-EAP-Request
   containing the EAP-Response [25] packet.

   Message Format

      <DIAMETER-EAP-Ind> ::= <DIAMETER Header, Command-Code = 270>
                             <Host-Name AVP>
                             <Destination-NAI>
                             <EAP-Payload AVP>
                             <User-Name AVP>
                             [<Timestamp AVP>
                              <Initialization-Vector AVP>
                              <Integrity-Check-Vector AVP>]


4.3  EAP-Payload AVP

   The EAP-Payload AVP (AVP Code 402) is of type Data and is used to
   encapsulate the actual EAP payload [25] that is being exchanged
   between the dial-up PPP client and the home DIAMETER server.





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5.0  DIAMETER Session Termination

   When a Network Access Server (NAS) receives an indication that a
   user's session is being disconnected (e.g. LCP Terminate is
   received), the NAS MUST issue a Session-Termination-Request (STR) [2]
   to its DIAMETER Server. This will ensure that any resources
   maintained on the servers is freed appropriately.

   Further, a NAS that receives a Session-Termination-Ind (STI) [2] MUST
   disconnect the PPP (or tunneling) session and respond with an STR
   message.


6.0  Legacy Authorization AVPs

   This section contains the various authorization AVPs that are also
   supported by the RADIUS protocol [1]. Use of these AVPs guarantees
   interoperability with a RADIUS infrastructure.


6.1  Service Identification AVPs

   This section contains the authorization AVPs that are needed to
   identify a service, and to allow the server to set constraints on a
   session.


6.1.1  NAS-Port AVP

   The NAS-Port AVP (AVP Code 5) is of type Integer32 and contains the
   physical port number of the NAS which is authenticating the user, and
   is normally only present in an authentication and/or authorization
   request. 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 (AVP Code 61) or both SHOULD be
   present in the request, if the NAS differentiates among its ports.


6.1.2  Service-Type AVP

   The Service-Type AVP (AVP Code 6) is of type Integer32 and contains
   the type of service the user has requested, or the type of service to
   be provided.  One such AVP MAY be present in an authentication and/or
   authorization request or response. A NAS is not required to implement
   all of these service types, and MUST treat unknown or unsupported
   Service-Types as though a response with a Result-Code other than
   DIAMETER-SUCCESS had been received instead.




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   When used in a request, the Service-Type AVP SHOULD be considered to
   be a hint to the 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. The following values have been defined
   for the Service-Type AVP:

   Login               1
      The user should be connected to a host.

   Framed              2
      A Framed Protocol should be started for the User, such as PPP or
      SLIP.

   Callback Login      3
      The user should be disconnected and called back, then connected to
      a host.

   Callback Framed     4
      The user should be disconnected and called back, then a Framed
      Protocol should be started for the User, such as PPP or SLIP.

   Outbound            5
      The user should be granted access to outgoing devices.

   Administrative      6
      The user should be granted access to the administrative interface
      to the NAS from which privileged commands can be executed.

   NAS Prompt          7
      The user should be provided a command prompt on the NAS from which
      non-privileged commands can be executed.

   Authenticate Only   8
      Only Authentication is requested, and no authorization information
      needs to be returned in the response.

   Callback NAS Prompt 9
      The user should be disconnected and called back, then provided a
      command prompt on the NAS from which non-privileged commands can
      be executed.


6.1.3  Filter-Id AVP

   The Filter-Id AVP (AVP Code 11) is of type String and contains the
   name of the filter list for this user. Zero or more Filter-Id AVPs
   MAY be sent in an authorization response.




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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.

   In non-RADIUS environments, it is strongly recommended that the
   Filter-Rule AVP be used instead.


6.1.4  Callback-Number AVP

   The Callback-Number AVP (AVP Code 19) is of type String and contains
   a dialing string to be used for callback. It MAY be used in an
   authentication and/or authorization request as a hint to the server
   that a Callback service is desired, but the server is not required to
   honor the hint in the corresponding response.

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


6.1.5  Callback-Id AVP

   The Callback-Id AVP (AVP Code 20) is of type String and contains the
   name of a place to be called, to be interpreted by the NAS. This AVP
   MAY be present in an authentication and/or authorization response.

   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.


6.1.6  Idle-Timeout AVP

   The Idle-Timeout AVP (AVP Code 28) is of type Integer32 and sets the
   maximum number of consecutive seconds of idle connection allowed to
   the user before termination of the session or prompt. It MAY be used
   in an authentication and/or authorization request (or challenge) as a
   hint to the server that an idle timeout is desired, but the server is
   not required to honor the hint in the corresponding response.


6.1.7  Called-Station-Id AVP

   The Called-Station-Id AVP (AVP Code 30) is of type String and allows
   the NAS to send in the request the phone number that the user called,
   using Dialed Number Identification (DNIS) or a similar technology.
   Note that this may be different from the phone number the call comes



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   in on. It SHOULD only be present in authentication and/or
   authorization requests.

   If the Request-Type AVP is set to authorization-only and the User-
   Name AVP is absent, the DIAMETER Server MAY 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.

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


6.1.8  Calling-Station-Id AVP

   The Calling-Station-Id AVP (AVP Code 31) is of type String and allows
   the NAS to send in the request the phone number that the call came
   from, using Automatic Number Identification (ANI) or a similar
   technology. It SHOULD only be present in authentication and/or
   authorization requests.


   If the Request-Type AVP is set to authorization-only and the User-
   Name AVP is absent, the DIAMETER Server MAY 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.

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


6.1.9  NAS-Port-Type AVP

   The NAS-Port-Type AVP (AVP Code 61) is of type Integer32 and contains
   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)
   AVP.  This AVP SHOULD only be used in authentication and/or
   authorization requests. This AVP MAY be combined with the NAS-Port
   AVP to assist in differentiating its ports.

   The following values are defined:
      0       Async
      1       Sync
      2       ISDN Sync
      3       ISDN Async V.120
      4       ISDN Async V.110
      5       Virtual
      6       PIAFS
      7       HDLC Clear Channel



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      8       X.25
      9       X.75
      10      G.3 Fax
      11      SDSL - Symmetric DSL
      12      ADSL-CAP - Asymmetric DSL, Carrierless Amplitude Phase Modulation
      13      ADSL-DMT - Asymmetric DSL, Discrete Multi-Tone
      14      IDSL - ISDN Digital Subscriber Line
      15      Ethernet
      16      xDSL
      17      Cable
      18      Wireless - Other
      19      Wireless - IEEE 802.11

   "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
   request might include NAS-Port-Type = Virtual as a hint to the
   DIAMETER server that the user was not on a physical port.


6.1.10  Port-Limit AVP

   The Port-Limit AVP (AVP Code 62) is of type Integer32 and sets the
   maximum number of ports to be provided to the user by the NAS.  It
   MAY be used in an authentication and/or authorization request as a
   hint to the server that multilink PPP [9] service is desired, but the
   server is not required to honor the hint in the corresponding
   response.


6.2  Framed Access Authorization AVPs

   This section contains the authorization AVPs that are necessary to
   support framed access, such as PPP, SLIP, etc.


6.2.1  Framed-Protocol AVP

   The Framed-Protocol AVP (AVP Code 7) is of type Integer32 and
   contains the framing to be used for framed access. This AVP MAY be
   present in both requests and responses. The following values are
   currently supported:

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



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      6      X.75 Synchronous


6.2.2  Framed-IP-Address AVP

   The Framed-IP-Address AVP (AVP Code 8) is of type Address and
   contains the address to be configured for the user. It MAY be used in
   an authorization request as a hint to the server that a specific
   address is desired, but the server is not required to honor the hint
   in the corresponding response.

   Two addresses have special significance; 0xFFFFFFFF and 0xFFFFFFFE.
   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).


6.2.3  Framed-IP-Netmask AVP

   The Framed-IP-Netmask AVP (AVP Code 9) is of type Address and
   contains the IP netmask to be configured for the user when the user
   is a router to a network.  It MAY be used in an authorization request
   as a hint to the server that a specific netmask is desired, but the
   server is not required to honor the hint in the corresponding
   response. This AVP MUST be present in a response if the request
   included this AVP with a value of 0xFFFFFFFF.


6.2.4  Framed-Routing AVP

   The Framed-Routing AVP (AVP Code 10) is of type Integer32 and
   contains the routing method for the user, when the user is a router
   to a network.  This AVP SHOULD only be present in authorization
   responses. The following values are defined for this AVP:

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


6.2.5  Framed-MTU AVP

   The Framed-MTU AVP (AVP Code 12) is of type Integer32 and contains
   the Maximum Transmission Unit to be configured for the user, when it
   is not negotiated by some other means (such as PPP). This AVP SHOULD
   only be present in authorization responses. The MTU value MUST be



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   between the range of 64 and 65535.


6.2.6  Framed-Compression AVP

   The Framed-Compression AVP (AVP Code 13) is of type Integer32 and
   contains the compression protocol to be used for the link. It MAY be
   used in an authorization request as a hint to the server that a
   specific compression type is desired, but the server is not required
   to honor the hint in the corresponding response.

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

   The following values are defined:
      0      None
      1      VJ TCP/IP header compression [7]
      2      IPX header compression
      3      Stac-LZS compression


6.2.7  Framed-IP-Route AVP

   The Framed-IP-Route AVP (AVP Code 22) is of type String and contains
   the routing information to be configured for the user on the NAS.
   Zero or more such AVPs MAY be present in an authorization response.

   The string 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 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.


6.2.8  Framed-IPX-Network AVP

   The Framed-IPX-Network AVP (AVP Code 23) is of type String and
   contains the IPX Network number to be configured for the user. It MAY
   be used in an authorization request as a hint to the server that a



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   specific address is desired, but the server is not required to honor
   the hint in the corresponding response.

   Two addresses have special significance; 0xFFFFFFFF and 0xFFFFFFFE.
   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 one or more IPX networks kept by the NAS).


6.2.9  Framed-AppleTalk-Link AVP

   The Framed-AppleTalk-Link AVP (AVP Code 37) is of type Integer32 and
   contains the AppleTalk network number which should be used for the
   serial link to the user, which is another AppleTalk router. This AVP
   MUST only be present in an authorization response and is never used
   when the user is not another router.

   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.


6.2.10  Framed-AppleTalk-Network AVP

   The Framed-AppleTalk-Network AVP (AVP Code 38) is of type Integer32
   and contains the AppleTalk Network number which the NAS should probe
   to allocate an AppleTalk node for the user.  This AVP MUST only be
   present in an authorization response and is never used when the user
   is not another router. Multiple instances of this AVP indicate that
   the NAS may probe using any of the network numbers specified.

   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.


6.2.11  Framed-AppleTalk-Zone AVP

   The Framed-AppleTalk-Zone AVP (AVP Code 39) is of type Data and
   contains the AppleTalk Default Zone to be used for this user. This
   AVP MUST only be present in an authorization response. Multiple
   instances of this AVP in the same message are not allowed.




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


6.3  Non-Framed Access Authorization AVPs

   This section contains the authorization AVPs that are needed to
   support terminal server functionality.


6.3.1  Login-IP-Host AVP

   The Login-IP-Host AVP (AVP Code 14) is of type Address and contains
   the system with which to connect the user, when the Login-Service AVP
   is included. It MAY be used in an authorization request as a hint to
   the server that a specific host is desired, but the server is not
   required to honor the hint in the corresponding response.

   Two addresses have special significance; 0xFFFFFFFF and 0xFFFFFFFE.
   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.


6.3.2  Login-Service AVP

   The Login-Service AVP (AVP Code 15) is of type Integer32 and contains
   the service which should be used to connect the user to the login
   host.  This AVP SHOULD only be present in authorization responses.

   The following values are defined:
      0      Telnet
      1      Rlogin
      2      TCP Clear
      3      PortMaster (proprietary)
      4      LAT
      5      X25-PAD
      6      X25-T3POS
      8      TCP Clear Quiet (supresses any NAS-generated connect string)


6.3.3  Login-TCP-Port AVP

   The Login-TCP-Port AVP (AVP Code 16) is of type Integer32 and
   contains the TCP port with which the user is to be connected, when
   the Login-Service AVP is also present. This AVP SHOULD only be
   present in authorization responses. The value MUST NOT be greater
   than 65535.



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6.3.4  Login-LAT-Service AVP

   The Login-LAT-Service AVP (AVP Code 34) is of type String and
   contains the system with which the user is to be connected by LAT. It
   MAY be used in an authorization request as a hint to the server that
   a specific service is desired, but the server is not required to
   honor the hint in the corresponding response. This AVP MUST only be
   present in the response if the Login-Service AVP states that LAT is
   desired.

   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).

   The String field 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.


6.3.5  Login-LAT-Node AVP

   The Login-LAT-Node AVP (AVP Code 35) is of type String and contains
   the Node with which the user is to be automatically connected by LAT.
   It MAY be used in an authorization request as a hint to the server
   that a specific LAT node is desired, but the server is not required
   to honor the hint in the corresponding response. This AVP MUST only
   be present in a response if the Service-Type AVP is set to LAT.

   The String field 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.


6.3.6  Login-LAT-Group AVP




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   The Login-LAT-Group AVP (AVP Code 36) is of type Data and contains a
   string identifying the LAT group codes which this user is authorized
   to use. It MAY be used in an authorization request as a hint to the
   server that a specific group is desired, but the server is not
   required to honor the hint in the corresponding response. This AVP
   MUST only be present in a response if the Service-Type AVP is set to
   LAT.

   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.

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


6.3.7  Login-LAT-Port AVP

   The Login-LAT-Port AVP (AVP Code 63) is of type String and contains
   the Port with which the user is to be connected by LAT. It MAY be
   used in an authorization request as a hint to the server that a
   specific port is desired, but the server is not required to honor the
   hint in the corresponding response. This AVP MUST only be present in
   a response if the Service-Type AVP is set to LAT.

   The String field 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.


6.4  Tunneling AVPs

   This section contains the authorization AVPs that are needed for a
   NAS to support tunneling users.


6.4.1  Tunnel-Type AVP

   The Tunnel-Type AVP (AVP Code 64) is of type Integer32 and contains
   the tunneling protocol(s) to be used (in the case of a tunnel



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   initiator) or the the tunneling protocol in use (in the case of a
   tunnel terminator).  It MAY be used in an authorization request as a
   hint to the server that a specific tunnel type is desired, but the
   server is not required to honor the hint in the corresponding
   response.

   The Tunnel-Type SHOULD also be present in the corresponding ADIF
   Record within the Accounting-Request.

   A tunnel initiator is not required to implement any of these tunnel
   types; if a tunnel initiator receives a response that contains only
   unknown or unsupported Tunnel-Types, the tunnel initiator MUST behave
   as though a response was received with the Result-Code indicating a
   failure.

   The following values have been defined:
      1      Point-to-Point Tunneling Protocol (PPTP) [14]
      2      Layer Two Forwarding (L2F) [15]
      3      Layer Two Tunneling Protocol (L2TP) [16]
      4      Ascend Tunnel Management Protocol (ATMP) [17]
      5      Virtual Tunneling Protocol (VTP)
      6      IP Authentication Header in the Tunnel-mode (AH) [18]
      7      IP-in-IP Encapsulation (IP-IP) [19]
      8      Minimal IP-in-IP Encapsulation (MIN-IP-IP) [20]
      9      IP Encapsulating Security Payload in the Tunnel-mode (ESP) [21]
      10     Generic Route Encapsulation (GRE) [22]
      11     Bay Dial Virtual Services (DVS)
      12     IP-in-IP Tunneling [23]


6.4.2  Tunnel-Medium-Type AVP

   The Tunnel-Medium-Type AVP (AVP Code 65) is of type Integer32 and
   contains the transport medium to use when creating a tunnel for those
   protocols (such as L2TP) that can operate over multiple transports.
   It MAY be used in an authorization request as a hint to the server
   that a specific medium is desired, but the server is not required to
   honor the hint in the corresponding response.

   The Value field is three octets and contains one of the values listed
   under "Address Family Numbers" in [10]. The value of most importance
   is (1) for IPv4 and (2) for IPv6.


6.4.3  Tunnel-Client-Endpoint AVP

   The Tunnel-Client-Endpoint AVP (AVP Code 66) is of type String and
   contains the address of the initiator end of the tunnel. It MAY be



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   used in an authorization request as a hint to the server that a
   specific endpoint is desired, but the server is not required to honor
   the hint in the corresponding response.

   This AVP SHOULD be included in the ADIF Record of the corresponding
   Accounting-Request messages, in which case it indicates the address
   from which the tunnel was initiated. This AVP, along with the
   Tunnel-Server-Endpoint and Session-Id AVP [2], MAY be used to provide
   a globally unique means to identify a tunnel for accounting and
   auditing purposes.

   If Tunnel-Medium-Type is IPv4 (1), then this string is either the
   fully qualified domain name (FQDN) of the tunnel client machine, or
   it is a "dotted-decimal" IP address.  Conformant implementations MUST
   support the dotted-decimal format and SHOULD support the FQDN format
   for IP addresses.

   If Tunnel-Medium-Type is IPv6 (2), then this string is either the
   FQDN of the tunnel client machine, or it is a text representation of
   the address in either the preferred or alternate form [5].
   Conformant implementations MUST support the preferred form and SHOULD
   support both the alternate text form and the FQDN format for IPv6
   addresses.

   If Tunnel-Medium-Type is neither IPv4 nor IPv6, this string is a tag
   referring to configuration data local to the DIAMETER client that
   describes the interface and medium-specific address to use.


6.4.4  Tunnel-Server-Endpoint AVP

   The Tunnel-Server-Endpoint AVP (AVP Code 67) is of String and
   contains the address of the server end of the tunnel. It MAY be used
   in an authorization request as a hint to the server that a specific
   endpoint is desired, but the server is not required to honor the hint
   in the corresponding response.

   This AVP SHOULD be included in the ADIF Record of the corresponding
   Accounting-Request messages, in which case it indicates the address
   from which the tunnel was initiated. This AVP, along with the
   Tunnel-Client-Endpoint and Session-Id AVP [2], MAY be used to provide
   a globally unique means to identify a tunnel for accounting and
   auditing purposes.

   If Tunnel-Medium-Type is IPv4 (1), then this string is either the
   fully qualified domain name (FQDN) of the tunnel client machine, or
   it is a "dotted-decimal" IP address.  Conformant implementations MUST
   support the dotted-decimal format and SHOULD support the FQDN format



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   for IP addresses.

   If Tunnel-Medium-Type is IPv6 (2), then this string is either the
   FQDN of the tunnel client machine, or it is a text representation of
   the address in either the preferred or alternate form [5].
   Conformant implementations MUST support the preferred form and SHOULD
   support both the alternate text form and the FQDN format for IPv6
   addresses.

   If Tunnel-Medium-Type is not IPv4 or IPv6, this string is a tag
   referring to configuration data local to the DIAMETER client that
   describes the interface and medium-specific address to use.


6.4.5  Tunnel-Password AVP

   The Tunnel-Password AVP (AVP Code 69) is of type Data and may contain
   a password to be used to authenticate to a remote server. This AVP
   MUST only be present in authorization responses in an encrypted form,
   using one of the methods described in [2] and [13].


6.4.6  Tunnel-Private-Group-ID AVP

   The Tunnel-Private-Group-ID AVP (AVP Code 81) is of type String and
   contains the group ID for a particular tunneled session. The Tunnel-
   Private-Group-ID AVP MAY be included in an authorization request if
   the tunnel initiator can pre-determine the group resulting from a
   particular connection and SHOULD be included in the authorization
   response if this tunnel session is to be treated as belonging to a
   particular private group. Private groups may be used to associate a
   tunneled session with a particular group of users.  For example, it
   MAY be used to facilitate routing of unregistered IP addresses
   through a particular interface.  This value SHOULD be included the
   corresponding ADIF-Record in the Accounting-Request which pertain to
   a tunneled session.


6.4.7  Tunnel-Assignment-ID AVP

   The Tunnel-Assignment-ID AVP (AVP Code 82) is of type String and is
   used to indicate to the tunnel initiator the particular tunnel to
   which a session is to be assigned.  Some tunneling protocols, such as
   PPTP and L2TP, allow for sessions between the same two tunnel
   endpoints to be multiplexed over the same tunnel and also for a given
   session to utilize its own dedicated tunnel. This attribute provides
   a mechanism for DIAMETER to be used to inform the tunnel initiator
   (e.g.  PAC, LAC) whether to assign the session to a multiplexed



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   tunnel or to a separate tunnel. Furthermore, it allows for sessions
   sharing multiplexed tunnels to be assigned to different multiplexed
   tunnels.

   A particular tunneling implementation may assign differing
   characteristics to particular tunnels.  For example, different
   tunnels may be assigned different QOS parameters.  Such tunnels may
   be used to carry either individual or multiple sessions.  The
   Tunnel-Assignment-ID attribute thus allows the DIAMETER server to
   indicate that a particular session is to be assigned to a tunnel that
   provides an appropriate level of service.  It is expected that any
   QOS-related DIAMETER tunneling attributes defined in the future that
   accompany this attribute will be associated by the tunnel initiator
   with the ID given by this attribute.  In the meantime, any semantic
   given to a particular ID string is a matter left to local
   configuration in the tunnel initiator.

   The Tunnel-Assignment-ID AVP is of significance only to DIAMETER and
   the tunnel initiator.  The ID it specifies is intended to be of only
   local use to DIAMETER and the tunnel initiator. The ID assigned by
   the tunnel initiator is not conveyed to the tunnel peer.

   This attribute MAY be included in authorization responses. The tunnel
   initiator receiving this attribute MAY choose to ignore it and assign
   the session to an arbitrary multiplexed or non-multiplexed tunnel
   between the desired endpoints.  This attribute SHOULD also be
   included in the corresponding ADIF-Record in the Accounting-Request
   messages which pertain to a tunneled session.

   If a tunnel initiator supports the Tunnel-Assignment-ID AVP, then it
   should assign a session to a tunnel in the following manner:

      - If this AVP is present and a tunnel exists between the specified
        endpoints with the specified ID, then the session should be
        assigned to that tunnel.

      - If this AVP is present and no tunnel exists between the
        specified endpoints with the specified ID, then a new tunnel
        should be established for the session and the specified ID
        should be associated with the new tunnel.

      - If this AVP is not present, then the session is assigned to an
        unnamed tunnel.  If an unnamed tunnel does not yet exist between
        the specified endpoints then it is established and used for this
        and subsequent sessions established without the Tunnel-
        Assignment-ID attribute.  A tunnel initiator MUST NOT assign a
        session for which a Tunnel-Assignment-ID AVP was not specified
        to a named tunnel (i.e. one that was initiated by a session



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        specifying this AVP).

   Note that the same ID may be used to name different tunnels if such
   tunnels are between different endpoints.


6.4.8  Tunnel-Preference AVP

   The Tunnel-Preference AVP (AVP Code 83) is of type Integer32 and is
   used to identify the relative preference assigned to each tunnel when
   more than one set of tunneling AVPs is returned within separete
   Grouped-AVP AVPs. It MAY be used in an authorization request as a
   hint to the server that a specific preference is desired, but the
   server is not required to honor the hint in the corresponding
   response.

   For example, suppose that AVPs describing two tunnels are returned by
   the server, one with a Tunnel-Type of PPTP and the other with a
   Tunnel-Type of L2TP.  If the tunnel initiator supports only one of
   the Tunnel-Types returned, it will initiate a tunnel of that type.
   If, however, it supports both tunnel protocols, it SHOULD use the
   value of the Tunnel-Preference AVP to decide which tunnel should be
   started.  The tunnel having the numerically lowest value in the Value
   field of this AVP SHOULD be given the highest preference.  The values
   assigned to two or more instances of the Tunnel-Preference AVP within
   a given authorization response MAY be identical.  In this case, the
   tunnel initiator SHOULD use locally configured metrics to decide
   which set of AVPs to use.


6.4.9  Tunnel-Client-Auth-ID AVP

   The Tunnel-Client-Auth-ID AVP (AVP Code 90) is of type String and
   specifies the name used by the tunnel initiator during the
   authentication phase of tunnel establishment.  It MAY be used in an
   authorization request as a hint to the server that a specific
   preference is desired, but the server is not required to honor the
   hint in the corresponding response. This AVP MUST be present in the
   authorization response if an authentication name other than the
   default is desired. This AVP SHOULD be included in the corresponding
   ADIF-Record of the Accounting-Request messages which pertain to a
   tunneled session.


6.4.10  Tunnel-Server-Auth-ID AVP

   The Tunnel-Server-Auth-ID AVP (AVP Code 91) is of type String and
   specifies the name used by the tunnel terminator during the



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   authentication phase of tunnel establishment. It MAY be used in an
   authorization request as a hint to the server that a specific
   preference is desired, but the server is not required to honor the
   hint in the corresponding response. This AVP MUST be present in the
   authorization response if an authentication name other than the
   default is desired. This AVP SHOULD be included in the corresponding
   ADIF-Record of the Accounting-Request messages which pertain to a
   tunneled session.


7.0  Interactions with Resource Management

   The Resource Management extension [31] provides the ability for a
   DIAMETER node to query a peer for session state information. The
   document states that service-specific extensions are responsible for
   specifying what AVPs are to be present in the Resource-Token [31]
   AVP.

   In addition to the AVPs listed in [31], the Resource-Token with the
   Extension-Id AVP set to one (1) MUST include the Service-Type AVP. In
   the event of a framed (PPP) user, the Framed-IP-Address and Framed-
   IPX-Network MUST be present if the corresponding network is being
   used. For Login users, the Login-IP-Host AVP and Login-Service AVP
   MUST be present. For tunneling users, the Tunnel-Type, Tunnel-
   Medium-Type, Tunnel-Client-Endpoint, and the Tunnel-Server-Endpoint
   AVPs MUST be present.


8.0  IANA Considerations

   The command codes defined in Sections 3.1 and 4.2 are values taken
   from the Command-Code [2] address space and extended in [13], [29]
   and [30]. IANA should record the values as defined in Sections 2.1
   and 4.2.

   The AVPs defined in section 2.1 were alllocated from from the AVP
   numbering space defined in [2], and extended in [13], [29] and [30].
   IANA should record the values as defined in Sections 2.1.

   The DIAMETER base protocol [2] reserves the first 255 AVPs for legacy
   RADIUS support [1]. The AVPs defined in section 2.2 are defined in
   [1], and no number assignment is necessary.


8.1  Request-Type AVP Values

   The Request-Type AVP (section 2.1.1) has a set of values that MUST be
   maintained by IANA. Values 1 through 3 are defined in this document.



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   The remaining values are available for assignment via Designated
   Expert [27].


9.0  Security Considerations

   This document does not contain any security protocol, but does
   discuss how PPP authentication protocols can be carried within the
   DIAMETER protocol. The PPP authentication protocols that are
   described are PAP, CHAP and EAP.

   The use of PAP SHOULD be discouraged, since it exposes user's
   passwords to possibly non-trusted entities. PAP is also frequently
   used for use with One-Time Passwords (OTP), which does not expose any
   security risks. However, it is highly recommended that OTP be
   supported through the EAP protocol.

   This document also describes how CHAP can be carried within the
   DIAMETER protocol, which is required for backward RADIUS
   compatibility. The CHAP protocol, as used in a RADIUS environment,
   facilitates authentication replay attacks, and therefore SHOULD NOT
   be used when EAP is available.


10.0  References


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

   [2]  Calhoun, Rubens, Akhtar, Guttman, "DIAMETER Base Protocol",
        draft-calhoun-diameter-17.txt, IETF work in progress, September
        2000.

   [3]  Aboba, Beadles, "The Network Access Identifier." RFC 2486. Janu-
        ary 1999.

   [4]  Aboba, Zorn, "Criteria for Evaluating Roaming Protocols", RFC
        2477, January 1999.

   [5]  Hinden, R., Deering, S., "IP Version 6 Addressing Architecture",
        RFC 2373, July 1998

   [6]  W. Simpson, "PPP Challenge Handshake Authentication Protocol
        (CHAP)", RFC 1994, August 1996.

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




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   [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] Reynolds, J., Postel, J., "Assigned Numbers", STD 2, RFC 1700,
        October 1994

   [11] Calhoun, Zorn, Pan, Akhtar, "DIAMETER Framework", draft-
        calhoun-diameter-framework-07.txt, IETF work in progress, April
        2000.

   [12] S. Bradner, "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [13] P. Calhoun, W. Bulley, S. Farrell, "DIAMETER Strong Security
        Extension", draft-calhoun-diameter-strong-crypto-05.txt, IETF
        work in progress, September 2000.

   [14] Hamzeh, K., Pall, G., Verthein, W., Taarud, J., Little, W.,
        Zorn, G., "Point-to-Point Tunneling Protocol (PPTP)", RFC 2637,
        July 1999

   [15] Valencia, A., Littlewood, M., Kolar, T., "Cisco Layer Two For-
        warding (Protocol) 'L2F'", RFC 2341, May 1998

   [16] Townsley, W. M., Valencia, A., Rubens, A., Pall, G. S., Zorn,
        G., Palter, B., "Layer Two Tunneling Protocol (L2TP)", RFC 2661,
        August 1999

   [17] Hamzeh, K., "Ascend Tunnel Management Protocol - ATMP", RFC
        2107, February 1997

   [18] Kent, S., Atkinson, R., "Security Architecture for the Internet
        Protocol", RFC 2401, November 1998

   [19] Perkins, C., "IP Encapsulation within IP", RFC 2003, October
        1996

   [20] Perkins, C., "Minimal Encapsulation within IP", RFC 2004,
        October 1996

   [21] Atkinson, R., "IP Encapsulating Security Payload (ESP)", RFC
        1827, August 1995




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   [22] Hanks, S., Li, T., Farinacci, D., Traina, P., "Generic Routing
        Encapsulation (GRE)", RFC 1701, October 1994

   [23] Simpson, W., "IP in IP Tunneling", RFC 1853, October 1995

   [24] M. Beadles, D. Mitton, "Criteria for Evaluating Network Access
        Server Protocols", draft-ietf-nasreq-criteria-05.txt, IETF work
        in progress, June 2000.

   [25] L. J. Blunk, J. R. Vollbrecht, "PPP Extensible Authentication
        Protocol (EAP)." RFC 2284, March 1998.

   [26] G. Zorn, P. R. Calhoun, "Limiting Fraud in Roaming", draft-
        ietf-roamops-fraud-limit-00.txt, IETF work in progress, May
        1999.

   [27] Narten, Alvestrand, "Guidelines for Writing an IANA Considera-
        tions Section in RFCs", BCP 26, RFC 2434, October 1998

   [28] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, W. Bulley, J.
        Haag, "DIAMETER Implementation Guidelines", draft-calhoun-
        diameter-impl-guide-03.txt, IETF work in progress, June 2000.

   [29] J. Arkko, P. Calhoun, P. Patel, G. Zorn, "DIAMETER Accounting
        Extension", draft-calhoun-diameter-accounting-08.txt, IETF work
        in progress, September 2000.

   [30] P. Calhoun, C. Perkins, "DIAMETER Mobile IP Extensions", draft-
        calhoun-diameter-mobileip-11.txt, IETF work in progress, Sep-
        tember 2000.

   [31] P. Calhoun, N. Greene, "DIAMETER Resource Management", draft-
        calhoun-diameter-res-mgmt-05.txt, IETF Work in Progress, Sep-
        tember 2000.


11.0  Acknowledgements

   The authors would also like to acknowledge the following people for
   their contribution in the development of the DIAMETER protocol:

   Bernard Aboba, Jari Arkko, William Bulley, Daniel C. Fox, Lol Grant,
   Ignacio Goyret, Nancy Greene, Peter Heitman, Paul Krumviede, Fergal
   Ladley, Ryan Moats, Victor Muslin, Kenneth Peirce, Sumit Vakil, John
   R. Vollbrecht, Jeff Weisberg and Glen Zorn


12.0  Authors' Addresses



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   Questions about this memo can be directed to:

      Pat R. Calhoun
      Network and Security Research Center, Sun Labs
      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.
      Building One, Suite 2000
      4251 Plymouth Road
      Ann Arbor, Michigan  48105-2785
      USA

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


      Allan C. Rubens
      Tut Systems, Inc.
      220 E. Huron, Suite 260
      Ann Arbor, MI 48104
      USA

       Phone:  +1 734-995-1697
      E-Mail:  arubens@tutsys.com


      Jeff Haag
      Cisco Systems
      7025 Kit Creek Road
      PO Box 14987
      Research Triangle Park, NC 27709

       Phone:  1-919-392-2353
      E-Mail:  haag@cisco.com


13.0  Full Copyright Statement




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   Copyright (C) The Internet Society (1999).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published and
   distributed, in whole or in part, without restriction of any kind,
   provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing the
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Calhoun et al.             expires March 2001                  [Page 39]


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