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Versions: 00 01 02 03 04 05 06 07 08 09                                 
INTERNET DRAFT                                                Jari Arkko
Category: Standards Track                              Oy LM Ericsson Ab
Title: draft-calhoun-diameter-accounting-01.txt           Pat R. Calhoun
Date: October 1999                                Sun Microsystems, Inc.
                                                            Pankaj Patel
                                                   Convergys Corporation
                                                               Glen Zorn
                                                   Microsoft Corporation


                     DIAMETER Accounting Extension



Status of this Memo

   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@ipass.com mailing list.

   Distribution of this memo is unlimited.

   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.


Abstract

   The DIAMETER protocol provides Authentication and Authorization for
   dial-up PPP clients [2] and for Mobile-IP [3]. The ROAMOPS WG has
   been working on an accounting data format, called Accounting Data
   Interchange Format (ADIF) [10], as a method to transfer accounting



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   information over a wide variety of transports. This document describes
   how ADIF can be securely transmitted over the DIAMETER protocol.


Table of Contents

      1.0  Introduction
            1.1  Copyright Statement
            1.2  Requirements language
            1.3  Changes in version 01
      2.0  Command Codes
            2.1  Accounting-Request
            2.2  Accounting-Answer
            2.3  Accounting-Poll-Ind
      3.0  DIAMETER AVPs
            3.1  Accounting-Record-Type
            3.2  ADIF-Record
            3.3  Accounting-Confirmation
            3.4  Session-Token
            3.5  Accounting-Interim-Interval
            3.6  Accounting-Delivery-Max-Batch
            3.7  Accounting-Delivery-Max-Delay
            3.8  Accounting-Record-Number
      4.0  Protocol overview
            4.1  Authorization-Server Directed Model
            4.2  Protocol Messages
            4.3  Fault Resilience
            4.4  Session Records
            4.5  Accounting in brokering environments
      5.0  IANA Considerations
      6.0  Acknowledgments
      7.0  References
      8.0  Authors' Addresses
      9.0  Full Copyright Statement


1.0  Introduction

   The DIAMETER protocol provides Authentication and Authorization for
   dial-up PPP clients [2] and for Mobile-IP [3]. The ROAMOPS WG has
   been working on an accounting data format, called Accounting Data
   Interchange Format (ADIF) [10], as a method to transfer accounting
   information over a wide variety of transports. This document
   describes how ADIF can be securely transmitted over the DIAMETER
   protocol.

   This document describes how Accounting Records can be transmitted
   within the DIAMETER protocol in a secure fashion, even when the



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   messages must traverse DIAMETER proxies [1, 9]. This extension allows
   for both real-time and batched accounting transfers.

   This document introduces AVPs that are very similar to some found in
   the base [1] and the end-to-end security extension [9]. However,
   since this extension requires that the AVPs in question must have
   bits set which are not currently permitted in both the stated drafts,
   a new version of the AVP has been defined here. However, a future
   version of this document may make use of the original AVPs once the
   [1] and [9] have been corrected. If there is interest in this
   extension, the impact of changing [1] and [9] must be carefully
   evaluated.

   The Extension number for this draft is five (5). This value is used
   in the Extension-Id Attribute value Pair (AVP) as defined in [7].


1.1  Copyright Statement

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


1.2  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 [6].


1.3  Changes in version 01

   This document contains several minor editor changes found during the
   DIAMETER Document Reading Party in addition to the following:

      - Removed the Accounting-Session-Id in favor for the Session-Id as
      described in the base protocol.

      - Removed the Accounting-Digital-Signature in favor for the
      Digital-Signature described in the secure proxy extension.

      - Renamed the Accounting-Certificate to Session-Token.

      - Removed the Accounting-Session-Id from the Session-Token

      - Removed the Session-Record accounting type.

      - Added the Accounting-Poll-Ind Command Code.




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      - Added the Accounting-Delivery-Max-Batch and Accounting-
      Delivery-Max-Delay AVPs.

      - Added the Accounting-Record-Number, which is a way to identify
      an accounting record.


2.0  Command Codes

   This section will define the Commands [1] for DIAMETER
   implementations supporting the Mobile IP extension.

      Command Name          Command Code
      -----------------------------------
      Accounting-Request        ???
      Accounting-Answer         ???
      Accounting-Poll-Ind       ???


2.1  Accounting-Request

   Description

      The Accounting-Request command is sent by a DIAMETER node in order
      to exchange accounting information with a peer. The Accounting
      information is contained within an ADIF record, as described in
      [10].

      The Accounting-request command MAY contain accounting information
      for more than a single session, which allows it to send batched
      accounting information. When the batch mode is used, the session-
      Id AVP [1] MUST be present and the Digital-Signature AVP [6] MAY
      be present, and MUST have a tag of the same value as the ADIF-
      Record AVP.

      The Accounting-Request message MAY contain the Accounting-
      Confirmation AVP, with the corresponding Digital-Signature AVP
      signed by the user's home AAA server, when the request is being
      issued to a broker that allows direct communication (see section
      4.5).

   Message Format

      <Accounting-Request> ::= <DIAMETER Header>
                               <Accounting-Request Command AVP>
                               <Host-IP-Address AVP>
                               [<Host-Name AVP>]
                               (<Session-Id AVP> &&



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                                <Accounting-Record-Type> &&
                                <Accounting-Record-Number> &&
                                <User-Name AVP> &&
                                [<Accounting-Confirmation AVP> &&
                                 <Digital-Signature AVP>] &&
                                <ADIF-Record AVP> &&
                                <Digital-Signature AVP>)
                               <Timestamp AVP>
                               <Nonce AVP>
                               {<Integrity-Check-Value AVP> ||
                                <Digital-Signature AVP> }

   The length of the DIAMETER Command AVP must be 12 when the Command
   Code is set to ??? (Accounting-Request).


2.2  Accounting-Answer

   Description

      The Accounting-Answer command is used to acknowledge an
      Accounting-Request command. The Accounting-Answer command contains
      the same Session-Id AVP that was sent in the Accounting-Request
      command, and the MD5 hash in Accounting-Confirmation AVP forms a
      confirmation that the right accounting record was accepted.  This
      can be signed using the Digital-Signature AVP for end-to-end
      message integrity and possible non-repudiation.

      Only the target DIAMETER Server, known as the home DIAMETER
      Server, SHOULD respond with the Accounting-Answer command.

      If the Accounting-Request command contained more than one ADIF-
      Record AVP, the Accounting-Answer SHOULD contain the same number
      of ADIF-Record AVPs. However, it is possible for the DIAMETER
      Server to acknowledge each ADIF-Record in a separate response.
      This allows the sender of the ADIF-Records to send a batch of
      records, whose final destination are different.

   Message Format

      <Accounting-Answer> ::= <DIAMETER Header>
                              <Accounting-Answer Command AVP>
                              <Result-Code AVP>
                              <Host-IP-Address AVP>
                              [<Host-Name AVP>]
                              (<Session-Id AVP> &&
                               <Accounting-Record-Number> &&
                               <Result-Code AVP> &&



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                               <Accounting-Confirmation AVP> &&
                               <Digital-Signature AVP>)
                              <Timestamp AVP>
                              <Nonce AVP>
                              {<Integrity-Check-Value AVP> ||
                               <Digital-Signature AVP> }

   The length of the DIAMETER Command AVP must be 12 when the Command
   Code is set to ??? (Accounting-Answer).


2.3  Accounting-Poll-Ind

   Description

      The Accounting-Poll-Ind command is sent by a DIAMETER Server in
      order to force the Client to send current accounting data. This
      data MUST include not yet sent accounting records from completed
      sessions, as well as INTERIM_RECORD records from all ongoing
      sessions.

      The Client MUST use Accounting-Request command to send the
      accounting data.

      The use of Accounting-Poll-Ind is useful in situations where a
      DIAMETER Server comes up after an unscheduled downtime, and wishes
      to synchronize with the Client(s) sooner than at the end of the
      next INTERIM_RECORD or at the end of a session. Accounting-Order
      SHOULD NOT be used in a roaming situation due to the excessive
      polling through the roaming network.

      Warning: The use of the Accounting-Poll-Ind message is discouraged
      in roaming networks, since it is unfeasible for a server to
      attempt to poll all of it's roaming partner's DIAMETER Clients.

   Message Format

      <Accounting-Poll-Ind> ::= <DIAMETER Header>
                                <Accounting-Poll-Ind Command AVP>
                                <Host-IP-Address AVP>
                                [<Host-Name AVP>]
                                <Timestamp AVP>
                                <Nonce AVP>
                                {<Integrity-Check-Value AVP> ||
                                 <Digital-Signature AVP> }


   The length of the DIAMETER Command AVP must be 12 when the Command



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   Code is set to ??? (Accounting-Poll-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    Definition in Section
      -------------------------------------------------------------------
      Accounting-Record-Type            ???                 3.1
      ADIF-Record                       ???                 3.2
      Accounting-Confirmation           ???                 3.3
      Session-Token                     ???                 3.4
      Accounting-Interim-Interval       ???                 3.5
      Accounting-Delivery-Max-Batch     ???                 3.6
      Accounting-Delivery-Max-Delay     ???                 3.7
      Accounting-Record-Number          ???                 3.8


3.1  Accounting-Record-Type

   Description

      The Accounting-Record-Type AVP contains the type of record that
      can be found in the ADIF-Record AVP.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      AVP Flags
         The 'M' bit MUST be set. The 'T' bit MAY be set if more than
         one Accounting record is being sent in an Accounting-Request
         message.  The 'P' bit MAY be set if end to end message
         integrity is required, but may not be necessary if the
         Digital-Signature is used.  The 'H', 'E', 'V' bits MUST NOT be
         set.

      Integer32
         The Integer32 field contains the record type that can be found



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         in the ADIF-Record AVP. The following values are currently
         defined:

            EVENT_RECORD                    1
               An Accounting Event Record is used to indicate a service
               of indivisible nature has occurred.  This record contains
               all information relevant to the service, and is the only
               record of the service.

            START_RECORD                    2
               An Accounting Start, Interim, and Stop Records are used
               to indicate that a service of a measurable length has
               been given. An Accounting Start Record is used to
               initiate an accounting session, and contains accounting
               information that is relevant to the initiation of the
               session.

            INTERIM_RECORD                  3
               An Interim Accounting Record contains cumulative
               accounting information for an existing Accounting
               session. Interim Accounting Records SHOULD be sent
               everytime a re-authentication or re-authorization occurs.

            STOP_RECORD                     4
               An Accounting Stop Record is sent to terminate an
               accounting session and contains cumulative accounting
               information relevant to the existing session.

         The selection of whether to use INTERIM_RECORD records is
         directed by the Accounting-Interim-Interval AVP.


3.2  ADIF-Record

   Description

      This attribute contains an ADIF record, as defined in [10].

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+




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      AVP Flags
         The 'M' bit MUST be set. The 'T' bit MAY be set if more than
         one Accounting record is being sent in an Accounting-Request
         message.  The 'P' bit MAY be set if end to end message
         integrity is required, but may not be necessary if the
         Digital-Signature is used.  The 'H', 'E', 'V' bits MUST NOT be
         set.

      Data
         The Data field contains an ADIF payload as defined in [10].


3.3  Accounting-Confirmation

   Description

      This AVP contains an MD5 hash of a previous ADIF-Record, and is
      used to confirm receipt of the ADIF-Record. When signed via the
      Digital-Signature, this AVP provides the sender of the
      Accounting-Request with proof that the receiver accepted the
      Accounting record.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+

      AVP Flags
         The 'M' bit MUST be set. The 'T' bit MAY be set if more than
         one Accounting record is being sent in an Accounting-Request
         message.  The 'P' bit MAY be set if end to end message
         integrity is required, but may not be necessary if the
         Digital-Signature is used.  The 'H', 'E', 'V' bits MUST NOT be
         set.

      Data
         The Data field contains an MD5 hash of the ADIF-Record AVP
         being confirmed.


3.4  Session-Token

   Description



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      The Session-Token AVP is created by the home DIAMETER server as a
      result of a successful Authentication and/or Authorization. This
      "token" is used in the subsequent Accounting-Request messages as a
      proof that the user was in fact authorized for the service. The
      document [7] and section 4.1 provides further information on this
      AVP.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Length of Session-Id     |      Length of User-Name      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Length of Digital-Signature  |  Digital-Signature Transform  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Session-Lifetime                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Timestamp                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Session-Id...         |         User-Name...          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Digital-Signature...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      AVP Flags
         The 'M' bit MUST be set. The 'T' bit MAY be set if more than
         one Accounting record is being sent in an Accounting-Request
         message.  The 'P' bit MAY be set if end to end message
         integrity is required, but may not be necessary if the
         Accounting-Digital-Signature is used.  The 'H', 'E', 'V' bits
         MUST NOT be set.

      Length of Session-Id
         This 16 bit field contains the length of the Session-Id field
         found in this AVP.

      Length of User-Name
         This 16 bit field contains the length of the User-Name field
         found in this AVP.

      Length of Digital-Signature
         This 16 bit field contains the length of the Digital-Signature
         field found in this AVP.

      Digital-Signature Transform



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         This 16 bit field contains the transform used to generate the
         Digital-Signature field, as defined in the Digital-Signature
         AVP in [9].

      Session-Lifetime
         This 32 bit field contains the number of seconds that the
         session has been autorized for. This field MUST be the same as
         the value of the Session-Timeout AVP [1].

      TimeStamp
         This 32 bit field contains a timestamp representing when this
         AVP was created. The format of this field is identical to the
         Timestamp AVP defined in [1].

      Session-Id
         This variable length field contains the Session-Id, and MUST be
         identical to the value found in the Session-Id AVP [1].

      User-Name
         This variable length field contains the User-Name and MUST be
         identical to the value of the User-Name AVP [1].

      Digital-Signature
         This variable length field contains a signature of the AVP's
         data, not including the AVP header and is generated using the
         transform specified in the Digital-Signature-Transform field.


3.5  Accounting-Interim-Interval

   Description

      The Accounting-Interim-Interval AVP is sent from the DIAMETER
      authenticating/authorizing server to the DIAMETER Client. The
      Client uses information in the AVP to decide how and when to
      produce accounting records. With different values in this AVP,
      service sessions can result in one, two, or two+N accounting
      records, based on the needs of the home-organization.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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      AVP Flags
         As defined in the DIAMETER Base Protocol.

      Integer32
         The following accounting record production behaviour is
         directed by the inclusion of this AVP:

            1. The omission of the Accounting-Interim-Interval AVP or
            its inclusion with Value field set to 0 means that
            EVENT_RECORD, START_RECORD, and STOP_RECORD are produced, as
            appropriate for the service.

            2. The inclusion of the AVP with Value field set to a non-
            zero value means that INTERIM_RECORD records MUST be
            produced between the START_RECORD and STOP_RECORD records.
            The Value field of this AVP is the nominal interval between
            these records in seconds. The Client MUST produce the first
            INTERIM_RECORD record roughly at the time when this nominal
            interval has elapsed from the START_RECORD, the next one
            again as the interval has elapsed once more, and so on until
            the session ends and a STOP_RECORD record is produced.

            The Client MUST ensure that the interim record production
            times are randomized so that large accounting message storms
            are not created either among records or around a common
            service start time.


3.6  Accounting-Delivery-Max-Batch

   Description

      This attribute is sent to a device as a response to an
      authorization request. It controls how accounting data is
      transferred to the accounting server. The attribute sets the
      requirements in terms of number of locally collected records
      before accounting data transfer SHOULD begin. The DIAMETER Client
      MAY deliver the data earlier due to satisfying requirements set by
      Accounting- Delivery-Max-Delay, device reboot, lack of memory, or
      explicit configuration. The DIAMETER Client MUST begin the
      transfer in the given limits unless prevented from doing so by
      network partitions, client or server failures, network congestion,
      or client overload.

   AVP Format






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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         AVP Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      AVP Flags
         As defined in the DIAMETER Base Protocol.

      Integer32
         The Integer32 field contains the number of accounting records
         that may be stored locally at the DIAMETER Client before data
         transfer SHOULD begin. Refer to section 4.1 for information on
         how a record is placed on a particular batch, and how different
         maximum batch and delay attributes may be given to different
         sessions.


3.7  Accounting-Delivery-Max-Delay

   Description

      This attribute is sent to a device as a response to an
      authorization request. It controls how accounting data is
      transferred to the accounting server. The attribute sets the
      requirements in terms of maximum delay before accounting data
      transfer SHOULD begin. The DIAMETER Client MAY deliver the data
      earlier due to satisfying requirements set by Accounting-
      Delivery-Max-Batch, device reboot, lack of memory, or explicit
      configuration. The DIAMETER Client MUST begin the transfer in the
      given limits unless prevented from doing so by network partitions,
      client or server failures, network congestion, or client overload.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      AVP Flags
         As defined in the DIAMETER Base Protocol.




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      Integer32
         The Integer32 field contains the number of seconds that may
         elapse before accounting data transfer SHOULD begin from the
         DIAMETER Client. Refer to section 4.1 for information on how a
         record is placed on a particular batch, and how different
         maximum batch and delay attributes may be given to different
         sessions.


3.8  Accounting-Record-Number

   Description

      The Accounting-Record-Number AVP identifies this record within one
      session. As Session-Id AVPs are globally unique, the combination
      of Session-Id and Accounting-Record- Number AVPs is also globally
      unique, and can be used in matching accounting records with
      confirmations.

   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 Header (AVP Code = ???)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Integer32                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      AVP Flags
         As defined in the DIAMETER Base Protocol.

      Integer32
         This number uniquely identifies the record within a session. An
         easy way to produce unique numbers is to set the value to 0 for
         records of type EVENT_RECORD and START_RECORD, and set the
         value to 1 for the first INTERIM_RECORD, 2 for the second, and
         so on until the value for STOP_RECORD is one more than for the
         last INTERIM_RECORD.


4.0  Protocol overview

   This accounting protocol is based on an authorization-server directed
   model with capabilities for both efficient batch and fast real-time
   delivery of accounting information. Several fault resilience methods
   [11] have been built in to the protocol in order minimize loss of
   accounting data in various fault situations and under different



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   assumptions about the capabilities of the used devices.


4.1  Authorization-Server Directed Model

   The authorization-server directed model means that at authorization
   time, the device generating the accounting data gets information from
   the authorization server regarding the way accounting data shall be
   forwarded. This information includes a certificate to prove that the
   session truly was authorized, as well as accounting record timeliness
   requirements.

   When the user's home DIAMETER Server successfully authenticates
   and/or authorizes a session, it generates the Session-Token AVP that
   is returned in the response. The document [7] describes a possible
   format for the AVP, which is also described in section 3.6.

   As discussed in [11], batch transfer of accounting data is more CPU-
   and bandwidth efficient than real-time transfer.  However, there are
   many applications where real-time transfer is a requirement for at
   least some of the accounting records.  These applications include
   roaming, where most (local) accounting records can be transferred in
   batch mode, but roaming (visiting) accounting records should be
   transferred fast due to the needs of credit limit checks and fraud
   detection. For these reasons this accounting protocol defines both
   batch and real-time transfer modes, and allows their use
   simultaneously. The authorization server (chain) directs the
   selection of proper transfer strategy, based on its knowledge of the
   user and relationships of roaming partnerships. The server (or
   proxies in between) use the Accounting-Delivery-Max-Batch,
   Accounting-Delivery-Max-Delay, and Accounting-Interim-Interval AVPs
   to control the operation of the DIAMETER Client. The first two
   attributes set the requirements in terms of number of records and
   maximum delay before accounting data transfer for this session SHOULD
   begin.  The DIAMETER Client MAY deliver the data earlier due to a
   full batch of records, device reboot, lack of memory, or explicit
   configuration. The DIAMETER Client MUST begin the transfer in the
   given limits unless prevented from doing so by network partitions,
   client or server failures, network congestion, or client overload.

   The Accounting-Interim-Interval AVP, when present, instructs the
   DIAMETER Client to produce accounting records continuously even
   during a session.

   Typically, the authorization server uses a few batching/real-time
   classes, such as the local users whose data might be transferred once
   in an hour and the roaming users whose data would be transferred
   immediately. Each Accounting-Delivery-Max-Batch / Accounting-



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   Delivery-Max-Delay AVP pair with different values forms one pool of
   accounting data in the DIAMETER Client. That is, a new record is
   placed to same pool as the previous one if the authorization server
   returned same values for both AVPs and the pool has not been emptied
   in between.


4.2  Protocol Messages

   The DIAMETER Client generating the accounting data will use the
   Accounting-Request message to send one or more accounting records to
   the DIAMETER Server. The Server MUST reply with the Accounting-Answer
   message with appropriate confirmations.

   It is possible that a DIAMETER Proxy breaks up a batch of accounting
   records and sends them towards different DIAMETER Home Servers. In
   this case it is possible that a separate Accounting-Answer message
   contain the response for each block.  Therefore, a Client MUST be
   prepared to handle this scenario.

   Upon receipt of an Accounting-Request, a home DIAMETER Server MUST
   generate a response. The response includes the Result-Code, which MAY
   contain an error if the ADIF-Record, or some other AVP, is not
   acceptable. Furthermore, an Accounting-Confirmation MUST be returned.
   The Accounting-Confirmation is an MD5 hash of the ADIF-Record data
   which is being confirmed.

   Each DIAMETER Accounting protocol message MAY be compressed using
   IPComp in order to reduce the used network bandwidth.  DIAMETER peers
   MUST use a negotiation mechanisms such as ISAKMP/IKE in order to
   ensure that both peers are able to handle IPComp. Note that it
   usually makes sense to compress only Accounting-Request messages with
   possibly lengthy ADIF data, not Accounting-Answer messages.


4.3  Fault Resilience

   DIAMETER Base protocol mechanisms are used to overcome small message
   loss and network faults of temporary nature.

   DIAMETER Clients MUST implement the use of alternate servers to guard
   against server failures and certain network failures. DIAMETER
   Servers or related off-line processing systems MUST detect duplicate
   accounting records caused by the sending of same record to several
   servers and duplication of messages in transit. This detection MUST
   be based on the inspection of Accounting-Record-Id and Host-IP-
   Address AVP pairs.




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   DIAMETER Clients MAY have non-volatile memory for the safe storage of
   accounting records over reboots or extended network failures, network
   partitions, and server failures. If such memory is available the
   Client SHOULD store new accounting records there as soon as the
   records are created and until a positive acknowledgement of their
   reception from the DIAMETER Server has been received. Upon a reboot,
   the Client MUST starting sending the records in the non-volatile
   memory to the accounting server with appropriate modifications in
   termination cause, session length, and other relevant information in
   the records.

   A further extension of this protocol may include AVPs to control how
   many accounting records may at most be stored in the DIAMETER Client
   without committing them to the non-volatile memory or transferring
   them to the DIAMETER Server.

   The Client SHOULD NOT remove the accounting data from any of its
   memory areas before the correct Accounting-Answer has been received.
   The Client MAY remove oldest, undelivered or yet unacknowledged
   accounting data if it runs out of resources such as memory. It is an
   implementation dependent matter for the client to accept new sessions
   under this condition.


4.4  Session Records

   In all accounting records the Session-Id AVP, ADIF-Record AVP, and
   User-Name AVPs MUST be present. If only one accounting record is
   present in the message, the whole message may be protected using the
   Digital-Signature, as defined in [9].

   However, if the accounting records are being in sent in batch mode,
   the sender can create several "blocks" of accounting records by
   making use of the AVP Tag field (bit 'T' [1]). Each block is
   individually signed, unless all blocks are destined for the same home
   DIAMETER Server.

   Different types of session records are sent depending on the actual
   type of accounted service and the authorization server's directions
   for interim accounting. If the accounted service is of an indivisible
   nature, then the Accounting-Record-Type AVP MUST be present and set
   to the value EVENT_RECORD. This can be used to account for services
   such as "send an e-mail to this wireless terminal".

   If the accounted service is of a measurable length, then the AVP MUST
   use the values START_RECORD, STOP_RECORD, and possibly,
   INTERIM_RECORD.  If the authorization server has directed interim
   accounting to be on but with no specified interim interval, two



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   accounting records MUST be generated for each service of type
   session.  When the initial Accounting-Request is sent for a given
   session is sent, the Accounting-Record-Type AVP MUST be set to the
   value START_RECORD.  When the last Accounting-Request is sent, the
   value MUST be STOP_RECORD.

   If a specified interim interval exists, the DIAMETER Client MUST
   produce additional records between the START_RECORD and STOP_RECORD,
   marked INTERIM_RECORD. The production of these records is directed
   both by Accounting-Interim-Interval as well as any re-authentication
   or -authorization of the session.  If a batch size of greater than 1
   has been specified by the authorization server, then the DIAMETER
   Client MUST ensure that new interim records overwrite previous
   interim records for the same session and batch as this reduces the
   amount of memory required to store the records. In effect, this means
   that interim records are delivered at least as often as dictated by
   Accounting-Delivery-Max-Delay.


4.5  Accounting in brokering environments

   The DIAMETER base protocol describes brokers that provide redirect
   services, by allowing AAA servers within a roaming consortium to
   directly communicate in a secure fashion. However, since brokers can
   also provide settlement services, it needs to be aware of the
   accounting information exchange. Historically, the thought was to
   have the broker "proxy" the accounting records from the local to the
   home network.

   A new model has been defined that allows the local AAA server to
   issue the Accounting-Request message to the home AAA server, which
   includes the ADIF-Record AVP with the corresponding Digital-Signature
   AVP. The home server generates the Accounting-Confirmation AVP and
   the Digital-Signature AVP, which is returned in the Accounting-Answer
   message. The local AAA server then forwards both the ADIF-Record and
   the Accounting-Confirmation AVPs with both Digital-Signature AVPs to
   the broker in an Accounting-Request message. The broker replies by
   issuing an Accounting-Answer message that includes its own
   Accounting-Confirmation and Digital-Signature AVPs.

   This new model eliminates the need for application end-to-end
   security, by allowing the peers to communicate directly, and reduces
   the latency that would otherwise be added through the proxy process.


5.0  IANA Considerations

   The numbers for the Command Code AVPs (section 2) is taken from the



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   numbering space defined for Command Codes in [1]. The numbers for the
   various AVPs defined in section 3 were taken from the AVP numbering
   space defined in [1].  The numbering for the AVP and Command Codes
   MUST NOT conflict with values specified in [1] and other DIAMETER
   related Internet Drafts.

   This document introduces the Accounting-Record-Type AVP, which may
   contain pre-defined values. This document defines the values 1-3.
   All remaining values are available for assignment via IETF Consensus
   [8].


6.0  Acknowledgments

   The authors would like to thank Nenad Trifunovic, Tony Johansson and
   Pankaj Patel for their participation in the Document Reading Party.
   Thanks to the various people that have contributed to accounting
   related requirements at the IETF's AAA Working Group and other
   related WGs.


7.0  References

   [1] P. R. Calhoun, A. Rubens, "DIAMETER Base Protocol",
       draft-calhoun-diameter-08.txt, Work in Progress,
       August 1999.
   [2] P. R. Calhoun, "DIAMETER Authentication Extension",
       draft-calhoun-diameter-auth-06.txt, Work in Progress,
       August 1999.
   [3] P. R. Calhoun, C. Perkins, "DIAMETER Mobile IP Extension",
       draft-calhoun-diameter-mobileip-02.txt, Work in Progress,
       August 1999.
   [4] C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote
       Authentication Dial In User Service (RADIUS)." RFC 2138,
       April 1997.
   [5] C. Rigney, "RADIUS Accounting." RFC 2139,  April 1997.
   [6] S. Bradner, "Key words for use in RFCs to Indicate
       Requirement Levels", BCP 14, RFC 2119, March 1997.
   [7] G. Zorn, P. R. Calhoun, "Limiting Fraud in Roaming",
       draft-ietf-roamops-fraud-limit-00.txt, May 1999.
   [8] Narten, Alvestrand,"Guidelines for Writing an IANA
       Considerations Section in RFCs", BCP 26, RFC 2434,
       October 1998
   [9] P. Calhoun, W. Bulley, "DIAMETER Proxy Server Extensions",
        draft-calhoun-diameter-proxy-02.txt, Work in Progress,
        August 1999.
   [10] B. Aboba, D. Lidyard, "The Accounting Data Interchange
       Format (ADIF)", draft-ietf-roamops-actng-05.txt,



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       Work in Progress, November 1998.
   [11] B. Aboba, J. Arkko. Introduction to Accounting Management.
        draft-aboba-acct-01.txt. Work in progress, June 1999.



8.0  Authors' Addresses

   Questions about this memo can be directed to:

      Jari Arkko
      Oy LM Ericsson Ab
      02420 Jorvas
      Finland

       Phone: +358 40 5079256
      E-Mail: Jari.Arkko@ericsson.com


      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


      Pankaj Patel
      Convergys Corporation
      4600 Montgomery Road
      Cincinnati, OH 45212
      USA

       Phone: 1-513-723-2018
      E-Mail: pankaj.patel@convergys.com


      Glen Zorn
      Microsoft Corporation
      One Microsoft Way
      Redmond, WA 98052
      USA

       Phone: 1-425-703-1559



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      E-Mail: gwz@acm.org


9.0  Full Copyright Statement

   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 implmentation 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 docu- ment itself may not be modified in any
   way, such as  by  removing  the copyright notice or references to the
   Internet Society or other Inter- net organizations, except as needed
   for  the  purpose  of  developing Internet standards in which case
   the procedures for copyrights defined in the Internet Standards
   process must be followed, or as required  to translate it into
   languages other than   English.  The limited permis- sions granted
   above are perpetual and  will  not  be  revoked  by  the Internet
   Society or its successors or assigns.  This document and the
   information contained herein is provided on an "AS IS" basis  and
   THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE
   DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
   LIMITED TO ANY  WAR- RANTY  THAT  THE  USE  OF THE INFORMATION HEREIN
   WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS  FOR  A PARTICULAR PURPOSE."























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