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RADIUS Working Group                                       Pat R. Calhoun
INTERNET DRAFT                                           3Com Corporation
Category: Internet Draft                                  Mark A. Beadles
Title: draft-ietf-radius-acct-interim-00.txt             CompuServe, Inc.
Date: July 1997                                            Alex Ratcliffe
                                                 UUNET Technologies, Inc.


                           RADIUS Accounting
                  Interim Accounting Record Extension


Status of this Memo

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

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

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

Abstract

   The RADIUS Accounting document [1] defines a mechanism which is used
   by a Network Access Server (NAS) to send accounting information to a
   RADIUS server. The current protocol defines a Start and Stop record.
   This document defines an interim record which is used to make the
   RADIUS accounting protocol more robust.

1.0 Introduction

   The current protocol defines a message which a NAS sends to the RADIUS
   server when a session begins, and a message when the session ends.
   All information which is necessary for the billing process



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INTERNET DRAFT                                                 July 1997


   (i.e. session time, number of bytes transfered, etc) are only
   available in the Accounting Stop message. Therefore if a NAS becomes
   unavailable for some time (i.e. power failure, reboot, network
   problem, etc...) it becomes impossible for a service provider to bill
   for sessions initiated on the NAS (this is especially important with
   long lived sessions).

   This document introduces a new accounting message which is sent from
   NAS to the RADIUS server which is called the interim accounting
   message. This message is sent in order to periodically update the
   RADIUS server with information pertaining to a specific session.

1.1.  Specification of Requirements

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

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

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

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

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


2.  Operation

   When a session is initiated, a NAS issues a RADIUS Start Accounting
   Request. The RADIUS Server processes the request and issues a
   response. However, if the RADIUS Server wishes to receive interim
   accounting information it needs to add a new RADIUS Attribute defined
   below which indicates the interval in seconds between interim
   messages.




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INTERNET DRAFT                                                 July 1997


   This scheme does not break backward interoperability since a RADIUS
   server not supporting this extension will simply not add the new
   Attribute. On the other hand, NAS' not supporting this extension
   will simply ignore the Attribute. This means that if a RADIUS
   Server uses the interim extension for other purposes
   (i.e. resource management) it MUST be aware of NAS' which do not
   support this extension.

   Note that all information in an interim message is cumulative (i.e.
   number of packets sent is the total since the beginning of the
   session, not since the last interim message).

   It is envisioned that an Interim Accounting record would contain
   all of the attributes normally found in an Accounting Stop message
   with the exception of the Acct-Term-Cause attribute.

   Since accounting packets are modified when retransmissions occur, it
   is recommended that the interval time restart only once the response
   from the RADIUS Server has been received (making sure that interim
   updates are not sent while retransmissions are pendig for a given
   session). A NAS COULD divide the interval time with the maximum
   number of retranmissions configured locally in order to determine the
   retransmission mechanism.

   Although this extension allows control from a central RADIUS Server,
   the authors wish to caution against using low interval values (i.e.
   5 seconds). In a NAS with large port densities, it can becomes a
   CPU intensive task as well as a waste of network bandwidth.


3.  Attributes

   This section defines the new RADIUS Attributes necessary to support
   the Interim Accounting extension.

3.1.  Acct-Status-Type

   Description

      This attribute indicates whether this Accounting-Request marks the
      beginning of the user service (Start) or the end (Stop).

      It MAY be used by the client to mark the start of accounting (for
      example, upon booting) by specifying Accounting-On and to mark the
      end of accounting (for example, just before a scheduled reboot) by
      specifying Accounting-Off.


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INTERNET DRAFT                                                 July 1997


      Additionally this attribute MAY indicate an interim update.

   A summary of the Acct-Status-Type attribute format is shown below.
   The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      40 for Acct-Status-Type.

   Length

      6

   Value

      The Value field is four octets.

       1      Start
       2      Stop
       3      Interim Update
       7      Accounting-On
       8      Accounting-Off

3.2.  Acct-Interim-Interval

   Description

      This attribute indicates the number of seconds between each interim
          update in seconds for this specific session.

   A summary of the Acct-Interim-Interval attribute format is shown
   below. The fields are transmitted from left to right.







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INTERNET DRAFT                                                 July 1997


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      ?? for Acct-Interim-Interval.

   Length

      6

   Value

      The Value field contains the number of seconds between each
      interim update to be sent from the NAS for this session. The
      value MUST NOT be smaller than 5.



























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INTERNET DRAFT                                                 July 1997


4.0 Contacts

   Pat R. Calhoun
   3Com Corporation
   1800 Central Ave.
   Mount Prospect, Il, 60056
   pcalhoun@usr.com
   (847) 342-6898

   Mark A. Beadles,
   Compuserve Corporation
   CompuServe, Inc.
   5000 Britton Rd.
   Hilliard, OH, 43026
   mbeadles@web.compuserve.com
   (614) 723-1941

   Alex Ratcliffe,
   UUNET Technologies, Inc,
   3060 Williams Drive,
   Fairfax, VA, 22032.
   alexr@uu.net.
   (703) 206 5698.


5.0 References

   [1]   Rigney, C., "RADIUS Accounting", RFC 2139, April 1997.

   [2]   Rigney, C., Rubens, A., Simpson, W., and Willens, S., "Remote
         Authentication Dial In User Service (RADIUS)", RFC 2138,
         April 1997.
















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