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Network Working Group N. Brownlee Request for Comments: 2924 The University of Auckland Category: Informational A. Blount

                                                       MetraTech Corp.
                                                        September 2000
              Accounting Attributes and Record Formats

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.


 This document summarises Internet Engineering Task Force (IETF) and
 International Telecommunication Union (ITU-T) documents related to
 Accounting.  A classification scheme for the Accounting Attributes in
 the summarised documents is presented.  Exchange formats for
 Accounting data records are discussed, as are advantages and
 disadvantages of integrated versus separate record formats and
 transport protocols.  This document discusses service definition
 independence, extensibility, and versioning.  Compound service
 definition capabilities are described.

Table of Contents

 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   2
 2. Terminology and Notation . . . . . . . . . . . . . . . . . . .   3
 3. Architecture Model . . . . . . . . . . . . . . . . . . . . . .   4
 4. IETF Documents . . . . . . . . . . . . . . . . . . . . . . . .   4
 4.1. RADIUS . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
 4.1.1. RADIUS Attributes  . . . . . . . . . . . . . . . . . . . .   5
 4.2. DIAMETER . . . . . . . . . . . . . . . . . . . . . . . . . .   6
 4.2.1. DIAMETER Attributes  . . . . . . . . . . . . . . . . . . .   7
 4.3. ROAMOPS  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
 4.4. RTFM . . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
 4.4.1. RTFM Attributes  . . . . . . . . . . . . . . . . . . . . .   9
 4.5. ISDN MIB . . . . . . . . . . . . . . . . . . . . . . . . . .  10
 4.5.1. ISDN Attributes  . . . . . . . . . . . . . . . . . . . . .  10
 4.6. AToMMIB  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
 4.6.1. AToMMIB Attributes . . . . . . . . . . . . . . . . . . . .  11

Brownlee & Blount Informational [Page 1] RFC 2924 Accounting Attributes and Record Formats September 2000

 4.7. QoS: RSVP and DIFFSERV . . . . . . . . . . . . . . . . . . .  12
 4.7.1. QoS: RSVP and DIFFSERV Attributes  . . . . . . . . . . . .  13
 5. ITU-T Documents  . . . . . . . . . . . . . . . . . . . . . . .  13
 5.1. Q.825: Call Detail Recording . . . . . . . . . . . . . . . .  13
 5.2. Q.825 Attributes . . . . . . . . . . . . . . . . . . . . . .  14
 6. Other Documents  . . . . . . . . . . . . . . . . . . . . . . .  18
 6.1. TIPHON: ETSI TS 101 321  . . . . . . . . . . . . . . . . . .  18
 6.2. MSIX . . . . . . . . . . . . . . . . . . . . . . . . . . . .  19
 7. Accounting File and Record Formats . . . . . . . . . . . . . .  19
 7.1. ASN.1 Records  . . . . . . . . . . . . . . . . . . . . . . .  19
 7.1.1. RTFM and AToMMIB . . . . . . . . . . . . . . . . . . . . .  19
 7.1.2. Q.825  . . . . . . . . . . . . . . . . . . . . . . . . . .  20
 7.2. Binary Records . . . . . . . . . . . . . . . . . . . . . . .  20
 7.2.1. RADIUS . . . . . . . . . . . . . . . . . . . . . . . . . .  20
 7.2.2. DIAMETER . . . . . . . . . . . . . . . . . . . . . . . . .  20
 7.3. Text Records . . . . . . . . . . . . . . . . . . . . . . . .  21
 7.3.1. ROAMOPS  . . . . . . . . . . . . . . . . . . . . . . . . .  21
 8. AAA Requirements . . . . . . . . . . . . . . . . . . . . . . .  22
 8.1. A Well-defined Set of Attributes . . . . . . . . . . . . . .  22
 8.2. A Simple Interchange Format  . . . . . . . . . . . . . . . .  23
 9. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
 9.1. Record Format vs. Protocol . . . . . . . . . . . . . . . . .  24
 9.2. Tagged, Typed Data . . . . . . . . . . . . . . . . . . . . .  24
 9.2.1. Standard Type Definitions  . . . . . . . . . . . . . . . .  25
 9.3. Transaction Identifiers  . . . . . . . . . . . . . . . . . .  26
 9.4. Service Definitions  . . . . . . . . . . . . . . . . . . . .  26
 9.4.1. Service Independence . . . . . . . . . . . . . . . . . . .  27
 9.4.2. Versioned Service Definitions  . . . . . . . . . . . . . .  29
 9.4.3. Relationships Among Usage Events . . . . . . . . . . . . .  29
 9.4.4. Service Namespace Management . . . . . . . . . . . . . . .  30
 10. Encodings . . . . . . . . . . . . . . . . . . . . . . . . . .  30
 11. Security Considerations . . . . . . . . . . . . . . . . . . .  31
 12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  31
 13. Authors' Addresses  . . . . . . . . . . . . . . . . . . . . .  35
 14. Full Copyright Statement  . . . . . . . . . . . . . . . . . .  36

1. Introduction

 This document summarises IETF and ITU-T documents related to
 Accounting.  For those documents which describe Accounting Attributes
 (i.e. quantities which can be measured and reported), an Attribute
 Summary is given.  Although several of the documents describe
 Attributes which are similar, no attempt is made to identify those
 which are the same in several documents.  An extensible
 classification scheme for AAA Accounting Attributes is proposed; it
 is a superset of the attributes in all the documents summarised.

Brownlee & Blount Informational [Page 2] RFC 2924 Accounting Attributes and Record Formats September 2000

 Many existing accounting record formats and protocols [RAD-ACT]
 [TIPHON] are of limited use due to their single-service descriptive
 facilities and lack of extensibility.  While some record formats and
 protocols support extensible attributes [RAD-ACT], none provide
 identification, type checking, or versioning support for defined
 groupings of attributes (service definitions).  This document makes a
 case for well-defined services.
 Advantages and disadvantages of integrated versus separate record
 formats and transport protocols are discussed.  This document
 discusses service definition independence, extensibility, and
 versioning.  Compound service definition capabilities are described.

2. Terminology and Notation

 The following terms are used throughout the document.
 Accounting Server
    A network element that accepts Usage Events from Service Elements.
    It acts as an interface to back-end rating, billing, and
    operations support systems.
 Attribute-Value Pair (AVP)
    A representation for a Usage Attribute consisting of the name of
    the Attribute and a value.
    A component of a Usage Event.  A Usage Event describing a phone
    call, for instance, might have a "duration" Property.
    A type of task that is performed by a Service Element for a
    Service Consumer.
 Service Consumer
    Client of a Service Element.  End-user of a network service.
 Service Definition
    A specification for a particular service.  It is composed of a
    name or other identifier, versioning information, and a collection
    of Properties.
 Service Element
    A network element that provides a service to Service Consumers.
    Examples include RAS devices, voice and fax gateways, conference

Brownlee & Blount Informational [Page 3] RFC 2924 Accounting Attributes and Record Formats September 2000

 Usage Attribute
    A component of a Usage Event that describes some metric of service
 Usage Event
    The description of an instance of service usage.

3. Architecture Model

 Service Elements provide Services to Service Consumers.  Before,
 while, and/or after services are provided, the Service Element
 reports Usage Events to an Accounting Server.  Alternately, the
 Accounting Server may query the Service Element for Usage Events.
 Usage events are sent singly or in bulk.
    +------------+       +-----------+              +------------+
    |  Service   |<----->|  Service  | Usage Events | Accounting |
    |  Consumer  |   +-->|  Element  |------------->|   Server   |
    +------------+   |   +-----------+              +------------+
    +------------+   |
    |  Service   |<--+
    |  Consumer  |
 Accounting Servers may forward Usage Events to other systems,
 possibly in other administrative domains.  These transfers are not
 addressed by this document.

4. IETF Documents

 In March 1999 there were at least 19 Internet Drafts and 8 RFCs
 concerned with Accounting.  These are summarised (by working group)
 in the following sections.


 The RADIUS protocol [RAD-PROT] carries authentication, authorization
 and configuration information between a Network Access Server (NAS)
 and an authentication server.  Requests and responses carried by the
 protocol are expressed in terms of RADIUS attributes such as User-
 Name, Service-Type, and so on.  These attributes provide the
 information needed by a RADIUS server to authenticate users and to
 establish authorized network service for them.
 The protocol was extended to carry accounting information between a
 NAS and a shared accounting server.  This was achieved by defining a
 set of RADIUS accounting attributes [RAD-ACT].

Brownlee & Blount Informational [Page 4] RFC 2924 Accounting Attributes and Record Formats September 2000

 RADIUS packets have a short header containing the RADIUS packet type
 and authenticator (sixteen octets) and length, followed by a sequence
 of (Type, Length, Value) triples, one for each attribute.
 RADIUS is very widely used, and a number of significant new
 extensions to it have been proposed.  For example [RAD-EXT] discusses
 extensions to implement the Extensible Authentication Protocol (EAP)
 and the Apple Remote Access Protocol (ARAP).  [RAD-TACC] discusses
 extensions to permit RADIUS to interwork effectively with tunnels
 using protocols such as PPTP and L2TP.

4.1.1. RADIUS Attributes

 Each RADIUS attribute is identified by an 8-bit number, referred to
 as the RADIUS Type field.  Up-to-date values of this field are
 specified in the most recent Assigned Numbers RFC [ASG-NBR], but the
 current list is as follows:
 RADIUS Attributes [RAD-PROT]             36  Login-LAT-Group
                                          37  Framed-AppleTalk-Link
     1  User-Name                         38  Framed-AppleTalk-Network
     2  User-Password                     39  Framed-AppleTalk-Zone
     3  CHAP-Password
     4  NAS-IP-Address                    60  CHAP-Challenge
     5  NAS-Port                          61  NAS-Port-Type
     6  Service-Type                      62  Port-Limit
     7  Framed-Protocol                   63  Login-LAT-Port
     8  Framed-IP-Address
     9  Framed-IP-Netmask              RADIUS Accounting Attributes
    10  Framed-Routing                 [RAD-ACT]
    11  Filter-Id
    12  Framed-MTU                        40  Acct-Status-Type
    13  Framed-Compression                41  Acct-Delay-Time
    14  Login-IP-Host                     42  Acct-Input-Octets
    15  Login-Service                     43  Acct-Output-Octets
    16  Login-TCP-Port                    44  Acct-Session-Id
    17  (unassigned)                      45  Acct-Authentic
    18  Reply-Message                     46  Acct-Session-Time
    19  Callback-Number                   47  Acct-Input-Packets
    20  Callback-Id                       48  Acct-Output-Packets
    21  (unassigned)                      49  Acct-Terminate-Cause
    22  Framed-Route                      50  Acct-Multi-Session-Id
    23  Framed-IPX-Network                51  Acct-Link-Count
    24  State
    25  Class                          RADIUS Extension Attributes
    26  Vendor-Specific                [RAD-EXT]
    27  Session-Timeout
    28  Idle-Timeout                      52  Acct-Input-Gigawords

Brownlee & Blount Informational [Page 5] RFC 2924 Accounting Attributes and Record Formats September 2000

    29  Termination-Action                53  Acct-Output-Gigawords
    30  Called-Station-Id                 54  Unused
    31  Calling-Station-Id                55  Event-Timestamp
    32  NAS-Identifier
    33  Proxy-State                       70  ARAP-Password
    34  Login-LAT-Service                 71  ARAP-Features
    35  Login-LAT-Node                    72  ARAP-Zone-Access
    73  ARAP-Security
    74  ARAP-Security-Data
    75  Password-Retry
    76  Prompt
    77  Connect-Info
    78  Configuration-Token
    79  EAP-Message
    80  Message-Authenticator
    84  ARAP-Challenge-Response
    85  Acct-Interim-Interval
    87  NAS-Port-Id
    88  Framed-Pool
 RADIUS Tunneling Attributes
    64  Tunnel-Type
    65  Tunnel-Medium-Type
    66  Tunnel-Client-Endpoint
    67  Tunnel-Server-Endpoint
    68  Acct-Tunnel-Connection
    69  Tunnel-Password
    81  Tunnel-Private-Group-ID
    82  Tunnel-Assignment-ID
    83  Tunnel-Preference
    90  Tunnel-Client-Auth-ID
    91  Tunnel-Server-Auth-ID


 The DIAMETER framework [DIAM-FRAM] defines a policy protocol used by
 clients to perform Policy, AAA and Resource Control.  This allows a
 single server to handle policies for many services.  The DIAMETER
 protocol consists of a header followed by objects.  Each object is
 encapsulated in a header known as an Attribute-Value Pair (AVP).

Brownlee & Blount Informational [Page 6] RFC 2924 Accounting Attributes and Record Formats September 2000

 DIAMETER defines a base protocol that specifies the header formats,
 security extensions and requirements as well as a small number of
 mandatory commands and AVPs.  A new service can extend DIAMETER by
 extending the base protocol to support new functionality.
 One key differentiator with DIAMETER is its inherent support for
 Inter-Server communication.  Although this can be achieved in a
 variety of ways, the most useful feature is the ability to "proxy"
 messages across a set of DIAMETER servers (known as a proxy chain).
 The DIAMETER Accounting Extension document [DIAM-ACT] extends
 DIAMETER by defining a protocol for securely transferring accounting
 records over the DIAMETER base protocol.  This includes the case
 where accounting records may be passed through one or more
 intermediate proxies, in accordance with the 'referral broker' model.
 The DIAMETER accounting protocol [DIAM-ACT] defines DIAMETER records
 for transferring an ADIF record (see below).  It introduces five new
 attributes (480..485) which specify the way in which accounting
 information is to be delivered between DIAMETER servers.

4.2.1. DIAMETER Attributes

 DIAMETER AVPs are identified by a 16-bit number defined in [DIAM-
 AUTH].  Since most of the AVPs found in that document were copied
 from the RADIUS protocol [RAD-PROT], it is possible to have both
 RADIUS and DIAMETER servers read the same dictionary and users files.
 The backward compatibility that DIAMETER offers is intended to
 facilitate deployment.  To this end, DIAMETER inherits the RADIUS
 attributes, and adds only a few of its own.
 In the list below attribute numbers which are used for RADIUS
 attributes but not for DIAMETER are indicated with a star (*).
 RADIUS attributes used by DIAMETER are not listed again here.
 The DIAMETER attributes are:
     4      (unassigned, *)
    17      (unassigned)
    21      (unassigned)
    24      (unassigned, *)
    25      (unassigned, *)
    27      (unassigned, *)
    32      (unassigned, *)
    33      (unassigned, *)
   280      Filter-Rule
   281      Framed-Password-Policy

Brownlee & Blount Informational [Page 7] RFC 2924 Accounting Attributes and Record Formats September 2000

   480      Accounting-Record-Type
   481      ADIF-Record
   482      Accounting-Interim-Interval
   483      Accounting-Delivery-Max-Batch
   484      Accounting-Delivery-Max-Delay
   485      Accounting-Record-Number
   600      SIP-Sequence
   601      SIP-Call-ID
   602      SIP-To
   603      SIP-From


 [ROAM-IMPL] reviews the design and functionality of existing roaming
 implementations.  "Roaming capability" may be loosely defined as the
 ability to use any one of multiple Internet service providers (ISPs),
 while maintaining a formal customer-vendor relationship with only
 one.  One requirement for successful roaming is the provision of
 effective accounting.
 [ROAM-ADIF] proposes a standard accounting record format, the
 Accounting Data Interchange Format (ADIF), which is designed to
 compactly represent accounting data in a protocol-independent manner.
 As a result, ADIF may be used to represent accounting data from any
 protocol using attribute value pairs (AVPs) or variable bindings.
 ADIF does not define accounting attributes of its own.  Instead, it
 gives examples of accounting records using the RADIUS accounting

4.4. RTFM

 The RTFM Architecture [RTFM-ARC] provides a general method of
 measuring network traffic flows between "metered traffic groups".
 Each RTFM flow has a set of "address" attributes, which define the
 traffic groups at each of the flow's end-points.
 As well as address attributes, each flow has traffic-related
 attributes, e.g. times of first and last packets, counts for packets
 and bytes in each direction.
 RTFM flow measurements are made by RTFM meters [RTFM-MIB] and
 collected by RTFM meter readers using SNMP.  The MIB uses a
 "DataPackage" convention, which specifies the attribute values to be
 read from a flow table row.  The meter returns the values for each

Brownlee & Blount Informational [Page 8] RFC 2924 Accounting Attributes and Record Formats September 2000

 required attribute within a BER-encoded sequence.  This means there
 is only one object identifier for the whole sequence, greatly
 reducing the number of bytes required to retrieve the data.

4.4.1. RTFM Attributes

 RTFM attributes are identified by a 16-bit attribute number.
 The RTFM Attributes are:
  0  Null
  1  Flow Subscript                Integer    Flow table info
  4  Source Interface              Integer    Source Address
  5  Source Adjacent Type          Integer
  6  Source Adjacent Address       String
  7  Source Adjacent Mask          String
  8  Source Peer Type              Integer
  9  Source Peer Address           String
 10  Source Peer Mask              String
 11  Source Trans Type             Integer
 12  Source Trans Address          String
 13  Source Trans Mask             String
 14  Destination Interface         Integer    Destination Address
 15  Destination Adjacent Type     Integer
 16  Destination Adjacent Address  String
 17  Destination AdjacentMask      String
 18  Destination PeerType          Integer
 19  Destination PeerAddress       String
 20  Destination PeerMask          String
 21  Destination TransType         Integer
 22  Destination TransAddress      String
 23  Destination TransMask         String
 26  Rule Set Number               Integer    Meter attribute
 27  Forward Bytes                 Integer    Source-to-Dest counters
 28  Forward Packets               Integer
 29  Reverse Bytes                 Integer    Dest-to-Source counters
 30  Reverse Packets               Integer
 31  First Time                    Timestamp  Activity times
 32  Last Active Time              Timestamp
 33  Source Subscriber ID          String     Session attributes
 34  Destination Subscriber ID     String
 35  Session ID                    String

Brownlee & Blount Informational [Page 9] RFC 2924 Accounting Attributes and Record Formats September 2000

 36  Source Class                  Integer    "Computed" attributes
 37  Destination Class             Integer
 38  Flow Class                    Integer
 39  Source Kind                   Integer
 40  Destination Kind              Integer
 41  Flow Kind                     Integer
 50  MatchingStoD                  Integer    PME variable
 51  v1                            Integer    Meter Variables
 52  v2                            Integer
 53  v3                            Integer
 54  v4                            Integer
 55  v5                            Integer
 65-127 "Extended" attributes
           (to be defined by the RTFM working group)


 The ISDN MIB [ISDN-MIB] defines a minimal set of managed objects for
 SNMP-based management of ISDN terminal interfaces.  It does not
 explicitly define anything related to accounting, however it does
 define isdnBearerChargedUnits as
    The number of charged units for the current or last connection.
    For incoming calls or if charging information is not supplied by
    the switch, the value of this object is zero.
 This allows for an ISDN switch to convert its traffic flow data (such
 as Call Connect Time) into charging data.

4.5.1. ISDN Attributes

 The relevant object in the MIB is the ISDN bearer table, which has
 entries in the following form:
 IsdnBearerEntry ::=
         isdnBearerChannelType           INTEGER,
         isdnBearerOperStatus            INTEGER,
         isdnBearerChannelNumber         INTEGER,
         isdnBearerPeerAddress           DisplayString,
         isdnBearerPeerSubAddress        DisplayString,
         isdnBearerCallOrigin            INTEGER,
         isdnBearerInfoType              INTEGER,
         isdnBearerMultirate             TruthValue,
         isdnBearerCallSetupTime         TimeStamp,

Brownlee & Blount Informational [Page 10] RFC 2924 Accounting Attributes and Record Formats September 2000

         isdnBearerCallConnectTime       TimeStamp,
         isdnBearerChargedUnits          Gauge32

4.6. AToMMIB

 The "ATM Accounting Information MIB" document [ATM-ACT] describes a
 large set of accounting objects for ATM connections.  An
 administrator may select objects from this set using a selector of
 the form (subtree, list) where "subtree" specifies an object
 identifier from the AToMMIB.  For each subtree there is a table
 holding values for each ATM connection.  The required connections are
 indicated by setting bits in "list", which is an octet string.  For
 example, the set containing the number of received cells for the
 first eight ATM connections would be selected by
 (atmAcctngReceivedCells, 0xFF).
 The Connection-Oriented Accounting MIB document [ATM-COLL] defines a
 MIB providing managed objects used for controlling the collection and
 storage of accounting information for connection-oriented networks
 such as ATM.  The accounting data is collected into files for later
 retrieval via a file transfer protocol.  Records within an accounting
 file are stored as BER strings [ASN1, BER].

4.6.1. AToMMIB Attributes

 Accounting data objects within the AToMMBIB are identified by the
 last integer in their object identifiers.
 The ATM accounting data objects are:
    1   atmAcctngConnectionType
    2   atmAcctngCastType
    3   atmAcctngIfName
    4   atmAcctngIfAlias
    5   atmAcctngVpi
    6   atmAcctngVci
    7   atmAcctngCallingParty
    8   atmAcctngCalledParty
    9   atmAcctngCallReference
   10   atmAcctngStartTime
   11   atmAcctngCollectionTime
   12   atmAcctngCollectMode
   13   atmAcctngReleaseCause
   14   atmAcctngServiceCategory
   15   atmAcctngTransmittedCells
   16   atmAcctngTransmittedClp0Cells
   17   atmAcctngReceivedCells

Brownlee & Blount Informational [Page 11] RFC 2924 Accounting Attributes and Record Formats September 2000

   18   atmAcctngReceivedClp0Cells
   19   atmAcctngTransmitTrafficDescriptorType
   20   atmAcctngTransmitTrafficDescriptorParam1
   21   atmAcctngTransmitTrafficDescriptorParam2
   22   atmAcctngTransmitTrafficDescriptorParam3
   23   atmAcctngTransmitTrafficDescriptorParam4
   24   atmAcctngTransmitTrafficDescriptorParam5
   25   atmAcctngReceiveTrafficDescriptorType
   26   atmAcctngReceiveTrafficDescriptorParam1
   27   atmAcctngReceiveTrafficDescriptorParam2
   28   atmAcctngReceiveTrafficDescriptorParam3
   29   atmAcctngReceiveTrafficDescriptorParam4
   30   atmAcctngReceiveTrafficDescriptorParam5
   31   atmAcctngCallingPartySubAddress
   32   atmAcctngCalledPartySubAddress
   33   atmAcctngRecordCrc16


 As we move towards providing more than simple "best effort"
 connectivity, there has been a tremendous surge of interest in (and
 work on) protocols to provide managed Quality of Service for Internet
 sessions.  This is of particular interest for the provision of
 "Integrated Services", i.e. the transport of audio, video, real-time,
 and classical data traffic within a single network infrastructure.
 Two approaches to this have emerged so far:
  1. the Integrated Services architecture (intserv) [IIS-ARC], with its

accompanying signaling protocol, RSVP [RSVP-ARC], and RSVP's

    Common Open Policy Service protocol, COPS [RAP-COPS]
  1. the Differentiated Services architecture (diffserv) [DSRV-ARC]
 RSVP is a signaling protocol that applications may use to request
 resources from the network.  The network responds by explicitly
 admitting or rejecting RSVP requests.  Certain applications that have
 quantifiable resource requirements express these requirements using
 intserv parameters [IIS-SPEC].
 Diffserv networks classify packets into one of a small number of
 aggregated flows or "classes", based on the diffserv codepoint (DSCP)
 in the packet's IP header.  At each diffserv router, packets are
 subjected to a "per-hop behavior" (PHB), which is invoked by the
 DSCP.  Since RSVP is purely a requirements signalling protocol it can
 also be used to request connections from a diffserv network [RS-DS-

Brownlee & Blount Informational [Page 12] RFC 2924 Accounting Attributes and Record Formats September 2000

4.7.1. RSVP and DIFFSERV Attributes

 A set of parameters for specifying a requested Quality of Service are
 given in [IIS-SPEC].  These have been turned into accounting
 attributes within RTFM [RTFM-NEWA] and within the RSVP MIB [RSVP-
 The RTFM QoS attributes are:
      98      QoSService
      99      QoSStyle
     100      QoSRate
     101      QoSSlackTerm
     102      QoSTokenBucketRate
     103      QoSTokenBucketSize
     104      QoSPeakDataRate
     105      QoSMinPolicedUnit
     106      QoSMaxPolicedUnit
 The RSVP MIB contains a large number of objects, arranged within the
 following sections:
     General Objects
     Session Statistics Table
     Session Sender Table
     Reservation Requests Received Table
     Reservation Requests Forwarded Table
     RSVP Interface Attributes Table
     RSVP Neighbor Table
 The Session tables contain information such as the numbers of senders
 and receivers for each session, while the Reservation Requests tables
 contain details of requests handled by the RSVP router.  There are
 too many objects to list here, but many of them could be used for
 accounting.  In particular, RSVP Requests contain the specification
 of the service parameters requested by a user; these, together with
 the actual usage data for the connection make up an accounting record
 for that usage.

5. ITU-T Documents

5.1. Q.825: Call Detail Recording

 ITU-T Recommendation Q.825 specifies how CDRs (Call Detail Records)
 are produced and managed in Network Elements for POTS, ISDN and IN
 (Intelligent Networks).
 Uses of Call Detail information for various purposes are discussed.

Brownlee & Blount Informational [Page 13] RFC 2924 Accounting Attributes and Record Formats September 2000

 Each call produces one or more records describing events that
 occurred during the life of a call.  Data may be produced in real
 time (single CDRs), near real-time (blocks of CDRs), or as batch
 files of CDRs.
 The information model for Call Detail Recording is formally described
 in terms of an Entity-Relationship model, and an object model
 specified in terms of GDMO templates (Guidelines for the Definition
 of Managed Objects).  Note that this model includes the ways in which
 CDRs are transported from the (NE) Network Element where they are
 generated to the OS (Operations System) where they are used.

5.2. Q.825 Attributes

 The following attributes are defined.  The explanations given are
 very brief summaries only, see [Q-825] for the complete text.
 1  accessDelivery
      Indicates that the call was delivered to the called subscriber
 2  accountCodeInput
      Account code (for billing), supplied by subscriber.
78  additionalParticipantInfo
      (No details given)
 5  b-PartyCategory
      Subscriber category for called subscriber.
 4  bearerService
      Bearer capability information (only for ISDN calls).
13  cDRPurpose
      Reason for triggering this Call Data Record.
70  callDetailDataId
      Unique identifier for the CallDetailData object.
79  callDuration
      Duration of call
 6  callIdentificationNumber
      Identification number for call; all records produced for this
      call have the same callIdenfificationNumber.
73  callStatus
      Identifies whether the call was answered or not.

Brownlee & Blount Informational [Page 14] RFC 2924 Accounting Attributes and Record Formats September 2000

 9  calledPartyNumber
      Telephone number of the called subscriber (may be a
      "diverted-to" or "translated" number.
 7  callingPartyCategory
      Calling subscriber category.
 8  callingPartyNumber
      Telephone number of the calling party.
10  callingPartyNumberNotScreened
      An additional, user-provided (not screened) number to the
      calling party.
11  callingPartyType
      Calling subscriber type.
74  carrierId
      Carrier ID to which the call is sent.
12  cause
      Cause and location value for the termination of the call.
14  chargedDirectoryNumber
      Charged directory number (where the charged participant
      element can't indicate the number).
16  chargedParticipant
      Participant to be charged for the usage.
15  chargingInformation
      Charging information generated by a Network Element which is
      capable of charging.
17  configurationMask
      Time consumption, e.g. from B-answer to termination time,
      between partial call records, etc.
18  conversationTime
      Time consumption from B-answer to end of call.
19  creationTriggerList
      List of trigger values which will create Call Detail data
75  dPC
      Destination point code (for analysis purposes).

Brownlee & Blount Informational [Page 15] RFC 2924 Accounting Attributes and Record Formats September 2000

20  dataValidity
      Indicates that the NE is having problems, contents of the
      generated Call Detail record is not reliable.
23  durationTimeACM
      Time consumption from seizure until received ACM.
21  durationTimeB-Answer
      Time consumption from seizure until B-answer.
22  durationTimeNoB-Answer
      Time from seizure to termination when no B-answer was
25  exchangeInfo
      Identity of exchange where Call Detail record was generated.
26  fallbackBearerService
      Fallback bearer capability information for a call.
27  glare
      Indicates if a glare condition was encountered.
31  iNServiceInformationList
      Contains information about the use of IN (Intelligent Network)
32  iNSpecificInformation
      Contains information about the use of one IN service.
33  iSUPPreferred
      Indicate whether an ISUP preference was requested.
28  immediateNotificationForUsageMetering
      Indicates that the Call Detail records requires
      immediate data transfer to the Operations System.
34  maxBlockSize
      Maximum number of Call Detail records in a block.
35  maxTimeInterval
      Maximum latency allowable for near-real-time Call Detail
      data delivery.
36  networkManagementControls
      Indicates which Traffic Management Control has affected
      the call.

Brownlee & Blount Informational [Page 16] RFC 2924 Accounting Attributes and Record Formats September 2000

37  networkProviderId
      Indicates the Network Provider for whom the CDR is generated.
76  oPC
      Originating point code for a failed call (for analysis
38  operatorSpecific1AdditionalNumber
40  operatorSpecific2AdditionalNumber
42  operatorSpecific3AdditionalNumber
      Operator-defined additional participant information.
39  operatorSpecific1Number
41  operatorSpecific2Number
43  operatorSpecific3Number
      Operator-defined participant information.
44  originalCalledNumber
      Telephone number of the original called party.
45  partialGeneration
      Included if the CDR (Call Detail record) output is partial.
      Such CDRs have a field indicating their partial record number.
77  participantInfo
      (No details given).
46  percentageToBeBilled
      Percentage to be billed when normal billing rules are
      not to be followed.
47  periodicTrigger
      Defines the intervals at which the CDR file should be created.
48  personalUserId
      Internationally unique personal User Identity (for UPT calls).
49  physicalLineCode
      Identifies the call subscriber's physical line.
50  progress
      Describes an event which occurred during the life of a call.
51  queueInfo
      Used to record usage of queueing resources with IN calls.

Brownlee & Blount Informational [Page 17] RFC 2924 Accounting Attributes and Record Formats September 2000

52  receivedDigits
      The digits dialed by the subscriber.  (Normally only included
      for customer care purposes).
53  recordExtensions
      Information elements added by network operators and/or
      manufacturers in addition to the standard ones above.

6. Other Documents

6.1. TIPHON: ETSI TS 101 321

 TIPHON [TIPHON] is an XML-based protocol, carried by HTTP, which
 handles accounting and authorization requests and responses.
 The following are elements selected from TIPHON's DTD that are used
 for accounting.
 <!ELEMENT Currency (#PCDATA)> <!ELEMENT Amount (#PCDATA)>
     Identifies a numeric value.  Expressed using the period (.) as a
     decimal separator with no punctuation as the thousands separator.
     Contains a call's H.323 CallID value, and is thus used to
     uniquely identify individual calls.
 <!ELEMENT Currency (#PCDATA)>
     Defines the financial currency in use for the parent element.
 <!ELEMENT DestinationInfo type ( e164 | h323 | url | email |
                                  transport | international |
                                  national | network | subscriber |
                                  abbreviated | e164prefix )
     Gives the primary identification of the destination for a call.
 <!ELEMENT Increment (#PCDATA)>
     Indicates the number of units being accounted.
     Indicates a type of service being priced, authorized, or
     reported.  An empty Service element indicates basic Internet
     telephony service, which is the only service type defined by
     V1.4.2 of the specification.  The specification notes that "Later
     revisions of this standard are expected to specify more enhanced
     service definitions to represent quality of service,
     availability, payment methods, etc."

Brownlee & Blount Informational [Page 18] RFC 2924 Accounting Attributes and Record Formats September 2000

 <!ELEMENT DestinationInfo type ( e164 | h323 | url | email |
                                  transport | international |
                                  national | network | subscriber |
                                  abbreviated | e164prefix)
     Gives the primary identification of the source of a call.
 <!ELEMENT Timestamp (#PCDATA)>
     A restricted form of [ISO-DATE] that indicates the time at which
     the component was generated.
 <!ELEMENT TransactionId (#PCDATA)>
     Contains an integer, decimal valued identifier assigned to a
     specific authorized transaction.
     Indicates the units by which pricing is measured or usage
     recorded.  It shall contain one of the following values:
         s      seconds
         p      packets (datagrams)
         byte   bytes
 <!Element UsageDetail ( Service, Amount, Increment, Unit ) >
     Collects information describing the usage of a service.

6.2. MSIX

 MSIX [MSIX-SPEC] is an XML-based protocol transported by HTTP that is
 used to make accounting service definitions and transmit service
 usage information.  As its service definitions are parameterized and
 dynamic, it makes no definition of services or attributes itself, but
 allows implementors to make their own.  It specifies only the base
 data types that attributes may take: STRING, UNISTRING, INT32, FLOAT,

7. Accounting File and Record Formats

7.1. ASN.1 Records

7.1.1. RTFM and AToMMIB

 RTFM and AToMMIB use ASN.1 Basic Encoding Rules (BER) to encode lists
 of attributes into accounting records.  RTFM uses SNMP to retrieve
 such records as BER strings, thus avoiding having to have an object
 identifier for every object.

Brownlee & Blount Informational [Page 19] RFC 2924 Accounting Attributes and Record Formats September 2000

 AToMMIB carries this a stage further by defining an accounting file
 format in ASN.1 and making it available for retrieval by a file
 transfer protocol, thereby providing a more efficient alternative to
 simply retrieving the records using SNMP.

7.1.2. Q.825

 A Q.825 Call Record is an ASN.1 SET containing a specified group of
 the Q.825 attributes.  Call records would presumably be encoded as
 BER strings before being collected for later processing.

7.2. Binary Records

7.2.1. RADIUS

 Radius packets carry a sequence of attributes and their values, as
 (Type, Length, Value) triples.  The format of the value field is one
 of four data types.
    string   0-253 octets
    address  32 bit value, most significant octet first.
    integer  32 bit value, most significant octet first.
    time     32 bit value, most significant octet first -- seconds
             since 00:00:00 GMT, January 1, 1970.  The standard
             Attributes do not use this data type but it is presented
             here for possible use within Vendor-Specific attributes.


 Each DIAMETER message consists of multiple AVP's that are 32-bit
 aligned, with the following format:
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    |                           AVP Code                            |
    |          AVP Length           |     Reserved        |P|T|V|R|M|
    |                        Vendor ID (opt)                        |
    |                           Tag (opt)                           |
    |    Data ...

Brownlee & Blount Informational [Page 20] RFC 2924 Accounting Attributes and Record Formats September 2000

       The AVP Code identifies the attribute uniquely.  If the Vendor-
       Specific bit is set, the AVP Code is allocated from the
       vendor's private address space.
       The first 256 AVP numbers are reserved for backward
       compatibility with RADIUS and are to be interpreted as per
       RADIUS [RAD-PROT].  AVP numbers 256 and above are used for
       DIAMETER, which are allocated by IANA.
    AVP Length
       A 16-bit field contains the total object length in bytes.
       Must always be a multiple of 4, and at least 8.
    AVP Flags
       P                      Protected bit
       T                      Tag bit
       V                      Vendor-ID bit
       R                      Reserved (MUST be set to 0)
       M                      Mandatory bit

7.3. Text Records

7.3.1. ROAMOPS

 ADIF (Accounting Data Interchange Format [ROAM-ADIF]) presents a
 general, text-based format for accounting data files, described in a
 straightforward BNF grammar.  Its file header contains a field
 indicating the default protocol from which accounting attributes are
 drawn.  If an attribute from another protocol is to be used, it is
 preceded by its protocol name, for example rtfm//27 would be RTFM's
 "forward bytes" attribute.  Comments in an ADIF file begin with a
 Example: An ADIF file encoding RADIUS accounting data
      version: 1
      device: server3
      description: Accounting Server 3
      date: 02 Mar 1999 12:19:01 -0500
      defaultProtocol: radius
      rdate: 02 Mar 1999 12:20:17 -0500
      5: 12

Brownlee & Blount Informational [Page 21] RFC 2924 Accounting Attributes and Record Formats September 2000

      61: 2
      40: 2
      41: 14
      42: 234732
      43: 15439
      44: 185
      45: 1
      46: 1238
      47: 153
      48: 148
      49: 11
      50: 73
      51: 2

8. AAA Requirements

8.1. A Well-Defined Set of Attributes

 AAA needs a well-defined set of attributes whose values are to be
 carried in records to or from accounting servers.
 Most of the existing sets of documents described above include a set
 of attributes, identified by small integers.  It is likely that these
 sets overlap, i.e. that some of them have attributes which represent
 the same quantity using different names in different sets.  This
 suggests it might be possible to produce a single combined set of
 "universal" accounting attributes, but such a "universal" set does
 not seem worthwhile.
 The ADIF approach of specifying a default protocol (from which
 attributes are assumed to come) and identifying any exceptions seems
 much more practical.  We therefore propose that AAA should use the

Brownlee & Blount Informational [Page 22] RFC 2924 Accounting Attributes and Record Formats September 2000

 ADIF convention (or something like it) to identify attributes,
 together with all the sets of attributes covered by the [ASG-NBR]

8.2. A Simple Interchange Format

 AAA needs a simple interchange file format, to be used for accounting
 data.  Several schemes for packaging and transporting such data have
 been described above.
 The SNMP-based ones fit well within the context of an SNMP-based
 network management system.  RTFM and AToMMIB provide ways to reduce
 the SNMP overhead for collecting data, and AToMMIB defines a complete
 file format.  Both provide good ways to collect accounting data.
 As an interchange format, however, ASN.1-based schemes suffer from
 being rather complex binary structures.  This means that one requires
 suitable tools to work with them, as compared to plain-text files
 where one can use existing text-based utilities.
 The binary schemes such as RADIUS and DIAMETER have simpler
 structures, but they too need purpose-built tools.  For general use
 they would need to be extended to allow them to use attributes from
 other protocols.
 From the point of view of being easy for humans to understand, ADIF
 seems very promising.  Of course any processing program would need a
 suitable ADIF input parser, but using plain-text files makes them
 much easier to understand.
 TIPHON's record format is specified by an XML DTD.  While XML
 representations have the advantages of being well-known, they are
 limited by XML's inability to specify type or other validity checking
 for information within the tags.  This situation will likely be
 improved by the XML Schema [XML-SCHM] efforts that are underway, but
 a stable reference is not yet available.

9. Issues

 It is generally agreed that there is a need for a standard record
 format and transport protocol for communication between Service
 Elements and Accounting Servers.
 There is less agreement on the following issues:
    o  Separate or integral record format and transport protocol
    o  Standard set of base data types
    o  Service definitions: part of the protocol or separately defined

Brownlee & Blount Informational [Page 23] RFC 2924 Accounting Attributes and Record Formats September 2000

    o  Service definition namespace management
 The following sections address these issues.

9.1. Record Format vs. Protocol

 All known Internet-centric billing protocols to date have an integral
 record format.  That is, the collection of Properties that describe a
 Usage Event are specified as an integral part of the protocol,
 typically as a part of a "submit" message that is used to transmit a
 Usage Event from a Service Entity to an Accounting Server.
 It may be advantageous to define a record format that is independent
 of the transport protocol.  Such a record format should support both
 representation of individual records and records in bulk, as Usage
 Events are often aggregated and transmitted in bulk.
 A separate record format is useful for record archiving and temporary
 file storage.  Multiple transport protocols may be defined without
 affecting the record format.  The task of auditing is made easier if
 a standard file format is defined.  If a canonical format is used,
 bulk records may be hashed with MD5 [MD5] or a similar function, for
 reliability and security purposes.
                                |  transport |
                                |   header   |
          +------------+        +------------+
          |            |        |            |
          |   Usage    |        |   Usage    |
          |  Event(s)  |        |  Event(s)  |
          |            |        |            |
          |            |        |            |
          +------------+        +------------+
                                |  trailer   |
          record format       transport protocol
 If the protocol is written such that it can transmit Usage Events in
 the record format, no record rewriting for transport is required.

9.2. Tagged, Typed Data

 Record formats and protocols use a combination of data locality and
 explicit tagging to identify data elements.  Mail [RFC822], for
 instance, defines a header block composed of several Attribute-Value
 Pairs, followed by a message body.  Each header field is explicitly

Brownlee & Blount Informational [Page 24] RFC 2924 Accounting Attributes and Record Formats September 2000

 tagged, but the order of the AVPs is undefined.  The message body is
 not tagged (except with an additional preceding blank line), and is
 found through its position in the message, which must be after all
 header fields.
 Some record formats make no use of tags--data elements are identified
 only by their position within a record structure.  While this
 practice provides for the least amount of record space overhead, it
 is difficult to later modify the record format by adding or removing
 elements, as all record readers will have to be altered to handle the
 change.  Tagged data allows old readers to detect unexpected tags and
 to detect if required data are missing.  If the overhead of carrying
 explicit tags can be borne, it is advantageous to use explicitly
 tagged data elements where possible.
 An AVP approach has proven useful in accounting.  RADIUS [RADIUS]
 uses numeric data type identifiers.  ETSI's TIPHON [TIPHON] uses XML
 For an AAA accounting record format, the authors suggest that each
 Property be named by a textual or numeric identifier and carry a
 value and a data type indicator, which governs interpretation of the
 value.  It may also be useful for each Property to carry a units of
 measure identifier.  The TIPHON specification takes this approach.
 TS 101 321 also carries an Increment field, which denominates the
 Property's Unit of Measure field.  Whether this additional
 convenience is necessary is a matter for discussion.
 It is not strictly necessary for each data record to carry data type,
 units of measure, or increments identifiers.  If this information is
 recorded in a record schema document that is referenced by each data
 record, each record may be validated against the schema without the
 overhead of carrying type information.

9.2.1. Standard Type Definitions

 It is useful to define a standard set of primitive data types to be
 used by the record format and protocol.  Looking at the prior art,
 DIAMETER supports Data (arbitrary octets), String (UTF-8), Address
 (32 or 128 bit), Integer32, Integer64, Time (32 bits, seconds since
 1970), and Complex.  MSIX [MSIX-SPEC] supports String, Unistring,
 Int32, Float, Double, Boolean, and Timestamp.  SMIv2 [SMI-V2] offers
 application-defined types Integer32, IpAddress, Counter32, Gauge32,
 Unsigned32, TimeTicks, Opaque, and Counter64.

Brownlee & Blount Informational [Page 25] RFC 2924 Accounting Attributes and Record Formats September 2000

 An appropriate set would likely include booleans, 32 and 64 bit
 signed integers, 32 and 64 bit floats, arbitrary octets, UTF-8 and
 UTF-16 strings, and ISO 8601:1988 [ISO-DATE] timestamps.  Fixed-
 precision numbers capable of representing currency amounts (with
 precision specified on both sides of the decimal point) have proven
 useful in accounting record formats, as they are immune to the
 precision problems that are encountered when one attempts to
 represent fixed-point amounts with floating point numbers.
 It may be worthwhile to consider the datatypes that are being
 specified by the W3C's "XML Schema Part 2: Datatypes" [XML-DATA]
 document.  That document specifies a rich set of base types, along
 with a mechanism to specify derivations that further constrain the
 base types.

9.3. Transaction Identifiers

 Each Usage Event requires its own unique identifier.
 It is expedient to allow Service Elements to create their own unique
 identifiers.  In this manner, Usage Events can be created and
 archived without the involvement of an Accounting Server or other
 central authority.
 A number of methods for creating unique identifiers are well known.
 One popular identifier is an amalgamation of a monotonically
 increasing sequence number, a large random value, a network element
 identifier, and a timestamp.  Another possible source of entropy is a
 hash value of all or part of the record itself.
 RFC 822 [MAIL], RFC 1036 [NEWS], and RFC 2445 [ICAL-CORE] give
 guidance on the creation of good unique identifiers.

9.4. Service Definitions

 A critical differentiator in accounting record formats and protocols
 is their capability to account for arbitrary service usage.  To date,
 no accounting record format or protocol that can handle arbitrary
 service definitions has achieved broad acceptance on the Internet.
 This section analyzes the issues in service definition and makes a
 case for a record format and protocol with the capability to carry
 Usage Events for rich, independently-defined services.

Brownlee & Blount Informational [Page 26] RFC 2924 Accounting Attributes and Record Formats September 2000

9.4.1. Service Independence

 It is informative to survey a number of popular Internet protocols
 and document encodings and examine their capacities for extension.
 These protocols can be categorized into two broad categories--"fully
 specified" protocols that have little provision for extension and
 "framework" protocols that are incomplete, but provide a basis for
 future extension when coupled with application documents.
 Examples of fully-specified protocols are NTP [NTP], NNTP [NNTP],
 RADIUS Accounting [RAD-ACT], and HTML [HTML].
 Aside from leaving some field values "reserved for future use", all
 of Network Time Protocol's fields are fixed-width and completely
 defined.  This is appropriate for a simple protocol that solves a
 simple problem.
 Network News Transfer Protocol [NEWS-PROT] specifies that further
 commands may be added, and requests that non-standard implementations
 use the "X-" experimental prefix so as to not conflict with future
 additions.  The content of news is 7-bit data, with the high-order
 bit cleared to 0.  Nothing further about the content is defined.
 There is no in-protocol facility for automating decoding of content
 We pay particular attention to RADIUS Accounting [RAD-ACT].  Perhaps
 the second most frequently heard complaint (after security
 shortcomings) about RADIUS Accounting is its preassigned and fixed
 set of "Types".  These are coded as a range of octets from 40 to 51
 and are as follows:
       40      Acct-Status-Type
       41      Acct-Delay-Time
       42      Acct-Input-Octets
       43      Acct-Output-Octets
       44      Acct-Session-Id
       45      Acct-Authentic
       46      Acct-Session-Time
       47      Acct-Input-Packets
       48      Acct-Output-Packets
       49      Acct-Terminate-Cause
       50      Acct-Multi-Session-Id
       51      Acct-Link-Count
 These identifiers were designed to account for packet-based network
 access service.  They are ill-suited for describing other services.
 While extension documents have specified additional types, the base

Brownlee & Blount Informational [Page 27] RFC 2924 Accounting Attributes and Record Formats September 2000

 protocol limits the type identifier to a single octet, limiting the
 total number of types to 256.
 HTML/2.0 [HTML] is mostly a fully-specified protocol, but with W3C's
 HTML/4.0, HTML is becoming more of a framework protocol.  HTML/2.0
 specified a fixed set of markups, with no provision for addition
 (without protocol revision).
 Examples of "framework" protocols and document encodings are HTTP,
 XML, and SNMP.
 HTTP/1.1 [HTTP] is somewhat similar to NNTP in that it is designed to
 transport arbitrary content.  It is different in that it supports
 description of that content through its Content-Type, Content-
 Encoding, Accept-Encoding, and Transfer-Encoding header fields.  New
 types of content can be designated and carried by HTTP/1.1 without
 modification to the HTTP protocol.
 XML [XML] is a preeminent general-purpose framework encoding.  DTD
 publishing is left to users.  There is no standard registry of DTDs.
 SNMP presents a successful example of a framework protocol.  SNMP's
 authors envisioned SNMP as a general management protocol, and allow
 extension through the use of private MIBs.  SNMP's ASN.1 MIBs are
 defined, published, and standardized without the necessity to modify
 the SNMP standard itself.  From "An Overview of SNMP" [SNMP-OVER]:
    It can easily be argued that SNMP has become prominent mainly from
    its ability to augment the standard set of MIB objects with new
    values specific for certain applications and devices.  Hence, new
    functionality can continuously be added to SNMP, since a standard
    method has been defined to incorporate that functionality into
    SNMP devices and network managers.
 Most accounting protocols are fully-specified, with either a
 completely defined service or set of services (RADIUS Accounting) or
 with one or more services defined and provision for "extension"
 services to be added to the protocol later (TIPHON).  While the
 latter is preferable, it may be preferable to take a more SNMP-like
 approach, where the accounting record format and protocol provide
 only a framework for service definition, and leave the task of
 service definition (and standardization) to separate efforts.  In
 this manner, the accounting protocol itself would not have to be
 modified to handle new services.

Brownlee & Blount Informational [Page 28] RFC 2924 Accounting Attributes and Record Formats September 2000

9.4.2. Versioned Service Definitions

 Versioning is a naming and compatibility issue.  Version identifiers
 are useful in service definition because they enable service
 definitions to be upgraded without a possibly awkward name change.
 They also enable possible compatibility between different versions of
 the same service.
 An example could be the service definition of a phone call.  Version
 1 might define Properties for the start time, duration, and called
 and calling party numbers.  Later, version 2 is defined, which
 augments the former service definition with a byte count.  An
 Accounting Server, aware only of Version 1, may accept Version 2
 records, discarding the additional information (forward
 compatibility).  Alternately, if an Accounting Server is made aware
 of version 2, it could optionally still accept version 1 records from
 Service Elements, provided the Accounting Sever does not require the
 additional information to properly account for service usage
 (backward compatibility).

9.4.3. Relationships Among Usage Events

 Accounting record formats and protocols to date do not sufficiently
 addressed "compound" service description.
 A compound service is a service that is described as a composition of
 other services.  A conference call, for example, may be described as
 a number of point-to-point calls to a conference bridge.  It is
 important to account for the individual calls, rather than just
 summing up an aggregate, both for auditing purposes and to enable
 differential rating.  If these calls are to be reported to the
 Accounting Server individually, the Usage Events require a shared
 identifier that can be used by the Accounting Server and other back-
 end systems to group the records together.
 In order for a Service Element to report compound events over time as
 a succession of individual Usage Events, the accounting protocol
 requires a facility to communicate that the compound event has
 started and stopped.  The "start" message can be implicit--the
 transmission of the first Usage Event will suffice.  An additional
 semaphore is required to tell the Accounting Server that the compound
 service is complete and may be further processed.  This is necessary
 to prevent the Accounting Server from prematurely processing compound
 events that overlap the end of a billing period.

Brownlee & Blount Informational [Page 29] RFC 2924 Accounting Attributes and Record Formats September 2000

 RADIUS Accounting has some provision for this sort of accounting with
 its "Acct-Multi-Session-Id" field.  Unfortunately, RADIUS
 Accounting's other shortcomings preclude it from being used in
 general purpose service usage description.

9.4.4. Service Namespace Management

 "Framework" protocols, as previously mentioned, do not define
 complete schema for their payload.  For interoperability to be
 achieved, it must be possible for:
    (1) content definers to specify definitions without conflicting
        with the names of other definitions
    (2) protocol users to find and use content definitions
 Condition (1) can be readily managed through IANA assignment or by
 using an existing namespace differentiator (for example, DNS).
 Condition (2) is harder, and places considerable burden on the
 implementors.  Their clients and servers must be able, statically or
 dynamically, to find and validate definitions, and manage versioning
 As previously mentioned, the XML specification provides no facility
 for DTD discovery or namespace management.  XML specifies only a
 document format, and as such does not need to specify support for
 more "protocol" oriented problems.
 For an accounting record format and protocol, an approach closer to
 SNMP's is useful.  SNMP uses an ISO-managed dotted-decimal namespace.
 An IANA-managed registry of service types is a possibility.  Another
 possibility, used by MSIX [MSIX-SPEC], is for Service Element
 creators to identify their services by concatenation of a new service
 name with existing unique identifier, such as a domain name.
 A standard record format for service definitions would make it
 possible for Service Element creators to directly supply accounting
 system managers with the required definitions, via the network or
 other means.

10. Encodings

 It may be useful to define more than one record encoding.
 A "verbose" XML encoding is easily implemented and records can be
 syntactically verified with existing tools.  "Human-readable"
 protocols tend to have an edge on "bitfield" protocols where ease of

Brownlee & Blount Informational [Page 30] RFC 2924 Accounting Attributes and Record Formats September 2000

 implementation is paramount and the application can tolerate any
 additional processing required to generate, parse, and transport the
 A alternative "compressed" encoding that makes minimal use of storage
 and processing may be useful in many contexts.
 There are disadvantages to supporting multiple encodings.
 Optionally-supported multiple encodings mandate the requirement for
 capabilities exchange between Service Element and Accounting Server.
 Also, implementations can tend to "drift apart", with one encoding
 better-supported than another.  Unless all encodings are mandatory,
 implementors may find they are unable to interoperate because they
 picked the wrong encoding.

11. Security Considerations

 This document summarises many existing IETF and ITU documents; please
 refer to the original documents for security considerations for their
 particular protocols.
 It must be possible for the accounting protocol to be carried by a
 secure transport.  A canonical record format is useful so that
 regeneration of secure record hashes is possible.
 When dealing with accounting data files, one must take care that
 their integrity and privacy are preserved.  This document, however,
 is only concerned with the format of such files.

12. References

 [ACC-BKG]   Mills, C., Hirsch, G. and G. Ruth, "Internet Accounting
             Background", RFC 1272, November 1991.
 [ASG-NBR]   Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,
             RFC 1700, October 1994.
 [ASN1]      Information processing systems - Open Systems
             Interconnection - Specification of Abstract Syntax
             Notation One (ASN.1), International Organization for
             Standardization, International Standard 8824, December
 [ATM-ACT]   McCloghrie, K., Heinanen, J., Greene, W. and A. Prasad,
             "Accounting Information for ATM Networks", RFC 2512,
             February 1999.

Brownlee & Blount Informational [Page 31] RFC 2924 Accounting Attributes and Record Formats September 2000

 [ATM-COLL]  McCloghrie, K., Heinanen, J., Greene, W. and A. Prasad, "
             Managed Objects for Controlling the Collection and
             Storage of Accounting Information for Connection-Oriented
             Networks", RFC 2513, February 1999.
 [BER]       Information processing systems - Open Systems
             Interconnection - Specification of Basic Encoding Rules
             for Abstract Notation One (ASN.1), International
             Organization for Standardization, International Standard
             8825, December 1987.
 [DIAM-ACT]  Arkko, J., Calhoun, P.R., Patel, P. and Zorn, G.,
             "DIAMETER Accounting Extension", Work in Progress.
 [DIAM-AUTH] Calhoun, P.R. and Bulley, W., "DIAMETER User
             Authentication Extensions", Work in Progress.
 [DIAM-FRAM] Calhoun, P.R., Zorn, G. and Pan, P., "DIAMETER Framework
             Document", Work in Progress.
 [DSRV-ARC]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.
             and W. Weiss, "An Architecture for Differentiated
             Services", RFC 2475, December 1998.
 [HTML]      Berners-Lee, T. and D. Connolly, "Hypertext Markup
             Language - 2.0", RFC 1866, November 1995.
 [HTTP]      Fielding, R., Gettys, J., Mogul, J. Frystyk, H. and T.
             Berners-Lee, "Hypertext Transfer Protocol--HTTP/1.1", RFC
             2068, January 1997.
 [ICAL-CORE] Dawson, F. and D. Stenerson, "Internet Calendaring and
             Scheduling Core Object Specification", RFC 2445, November
 [IIS-ARC]   Braden, R., Clark, D. and S. Shenker, "Integrated
             Services in the Internet Architecture: an Overview", RFC
             1633, June 1994.
 [IIS-SPEC]  Shenker, S., Partridge, C. and R. Guerin, "Specification
             of Guaranteed Quality of Service", RFC 2212, September
 [ISDN-MIB]  Roeck, G., "ISDN Management Information Base using
             SMIv2", RFC 2127, March 1997.

Brownlee & Blount Informational [Page 32] RFC 2924 Accounting Attributes and Record Formats September 2000

 [ISO-DATE]  "Data elements and interchange formats -- Information
             interchange -- Representation of dates and times", ISO
             TEXT MESSAGES", STD 11, RFC 822, August 1982.
 [MD5]       Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
             April 1992.
 [MSIX-SPEC] Blount, A. and D. Young, "Metered Service Information
             Exchange 1.2", Work in Progress.
 [NEWS-MSGS] Horton, M. and R. Adams, "Standard for Interchange of
             USENET Messages", RFC 1036, December 1987.
 [NEWS-PROT] Kantor, B. and P. Lapsley, "Network News Transfer
             Protocol", RFC 977, February 1986.
 [NTP]       Mills, D., "Network Time Protocol (NTP)", RFC 958,
             September 1985.
 [Q-825]     "Specification of TMN applications at the Q3 interface:
             Call detail recording", ITU-T Recommendation Q.825, 1998.
 [RAD-ACT]   Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
 [RAD-EXT]   Rigney, C., Willats, W. and Calhoun, P., "RADIUS
             Extensions", RFC 2869, June 2000.
 [RAD-PROT]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
             "Remote Authentication Dial In User Service (RADIUS)",
             RFC 2865, June 2000.
 [RAD-TACC]  Zorn, G., Mitton, D. and A. Aboba, "RADIUS Accounting
             Modifications for Tunnel Protocol Support", RFC 2867,
             June 2000.
 [RAP-COPS]  Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.
             and A. Sastry, "The COPS (Common Open Policy Service)
             Protocol", RFC 2748, January 2000.
 [ROAM-ADIF] Aboba, B. and D. Lidyard, "The Accounting Data
             Interchange Format (ADIF)", Work in Progress.
 [ROAM-IMPL] Aboba, B., Lu, J., Alsop, J., Ding, J. and W. Wang,
             "Review of Roaming Implementations", RFC 2194, September

Brownlee & Blount Informational [Page 33] RFC 2924 Accounting Attributes and Record Formats September 2000

 [RS-DS-OP]  Bernet, Y., Yavatkar, R., Ford, P., Baker, F., Zhang, L.,
             Speer, M., Braden, R., Davie, B., Wroclawski, J. and E.
             Felstaine, "A Framework For Integrated Services Operation
             Over Diffserv Networks", Work in Progress.
 [RSVP-ARC]  Braden, R., Zhang, L., Berson, S., Herzog, S. and S.
             Jamin, "Resource Reservation Protocol (RSVP) Version 1
             Functional Specification", RFC 2205, September 1997.
 [RSVP-MIB]  Baker, F., Krawczyk, J. and A. Sastry, "RSVP Management
             Information Base using SMIv2", RFC 2206, September 1997.
 [RTFM-ARC]  Brownlee, N., Mills, C. and G. Ruth, "Traffic Flow
             Measurement: Architecture", RFC 2722, October 1999.
 [RTFM-MIB]  Brownlee, N., "Traffic Flow Measurement: Meter MIB",
             Measurement: Architecture", RFC 2720, October 1999.
 [RTFM-NEWA] Handelman, S., Brownlee, N., Ruth, G. and S. Stibler,
             "New Attributes for Traffic Flow Measurement", RFC 2724,
             October 1999.
 [SIP-PROT]  Handley, M., Schulzrinne, H., Schooler, E. and J.
             Rosenberg, "SIP: Session Initiation Protocol", RFC 2543,
             March 1999.
 [SMI-V2]    McCloghrie, K., Perkins, D. and J. Schoenwaelder,
             "Structure of Management Information Version 2 (SMIv2)",
             STD 58, RFC 2578, April 1999.
 [SNMP-OVER] "AN OVERVIEW OF SNMP V2.0", Diversified Data Resources,
             Inc.,, 1999.
 [TIPHON]    "Telecommunications and Internet Protocol Harmonization
             Over Networks (TIPHON); Inter-domain pricing,
             authorization, and usage exchange", TS 101 321 V1.4.2,
             December 1998.
 [XML]       Bray, T., J. Paoli, and C. Sperberg-McQueen, "Extensible
             Markup Language (XML) 1.0", W3C Recommendation, February

Brownlee & Blount Informational [Page 34] RFC 2924 Accounting Attributes and Record Formats September 2000

 [XML-DATA]  "XML Schema Part 2: Datatypes", W3C Working Draft 07
             April 2000, April 2000.
 [XML-SCHM]  "XML Schema Part 1: Structures", W3C Working Draft 7
             April 2000, April 2000.

13. Authors' Addresses

 Nevil Brownlee
 Information Technology Systems & Services
 The University of Auckland
 Phone: +64 9 373 7599 x8941
 Alan Blount
 MetraTech Corp.
 330 Bear Hill Road
 Waltham, MA 02451

Brownlee & Blount Informational [Page 35] RFC 2924 Accounting Attributes and Record Formats September 2000

14. Full Copyright Statement

 Copyright (C) The Internet Society (2000).  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 copyright notice or references to the Internet Society or other
 Internet 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
 The limited permissions 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


 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Brownlee & Blount Informational [Page 36]

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