One document matched: draft-ietf-aaa-diameter-cc-05.txt
Differences from draft-ietf-aaa-diameter-cc-04.txt
AAA Working Group
Internet Draft Harri Hakala
Document: draft-ietf-aaa-diameter-cc-05.txt Leena Mattila
Expires: November 13, 2004 Ericsson
Juha-Pekka Koskinen
Marco Stura
John Loughney
Nokia
May 14, 2004
Diameter Credit-Control Application
Status of this memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
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This document is a product of the Authentication, Authorization and
Accounting (AAA) Working Group of the Internet Engineering Task Force
(IETF). Comments are welcome should be submitted to the mailing list
aaa-wg@merit.edu.
Abstract
This document specifies a DIAMETER application that can be used to
implement real-time credit-control for a variety of end user services
such as network access, Session Initiation Protocol (SIP) services,
messaging services, download services etc.
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1. Introduction...................................................5
1.1 Requirements language......................................5
1.2 Terminology................................................6
1.3 Advertising application support............................7
2. Architecture Models............................................8
3. Credit-Control Messages........................................9
3.1 Credit-Control-Request (CCR) Command......................10
3.2 Credit-Control-Answer (CCA) Command.......................11
4. Credit Control Application Overview...........................12
4.1 Service-Specific Rating Input and Interoperability........13
5. Session Based Credit-control..................................15
5.1 General Principles........................................15
5.2 First Interrogation.......................................20
5.3 Intermediate Interrogation................................26
5.4 Final Interrogation.......................................28
5.5 Server-Initiated Credit Re-Authorization..................29
5.6 Graceful Service Termination..............................31
5.7 Failure Procedures........................................36
6. One Time Event................................................39
6.1 Service Price Enquiry.....................................40
6.2 Balance Check.............................................40
6.3 Direct Debiting...........................................41
6.4 Refund....................................................42
6.5 Failure Procedure.........................................42
7. Credit Control Application State Machine......................44
8. Credit Control AVPs...........................................53
8.1 CC-Correlation-Id AVP.....................................55
8.2 CC-Request-Number AVP.....................................55
8.3 CC-Request-Type AVP.......................................56
8.4 CC-Session-Failover AVP...................................57
8.5 CC-Sub-Session-Id AVP.....................................57
8.6 Check-Balance-Result AVP..................................57
8.7 Cost-Information AVP......................................58
8.8 Unit-Value AVP............................................59
8.9 Exponent AVP..............................................59
8.10 Value-Digits AVP.........................................59
8.11 Currency-Code AVP........................................59
8.12 Cost-Unit AVP............................................60
8.13 Credit-Control AVP.......................................60
8.14 Credit-Control-Failure-Handling AVP......................60
8.15 Direct-Debiting-Failure-Handling AVP.....................61
8.16 Multiple-Services-Credit-Control AVP.....................62
8.17 Granted-Service-Unit AVP.................................63
8.18 Requested-Service-Unit AVP...............................64
8.19 Used-Service-Unit AVP....................................64
8.20 Tariff-Time-Change AVP...................................65
8.21 CC-Time AVP..............................................65
8.22 CC-Money AVP.............................................65
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8.23 CC-Total-Octets AVP......................................65
8.24 CC-Input-Octets AVP......................................65
8.25 CC-Output-Octets AVP.....................................66
8.26 CC-Service-Specific-Units AVP............................66
8.27 Tariff-Change-Usage AVP..................................66
8.28 Service-Identifier AVP...................................67
8.29 Rating-Group AVP.........................................67
8.30 G-S-U-Pool-Reference AVP.................................68
8.31 G-S-U-Pool-Identifier AVP................................68
8.32 CC-Unit-Type AVP.........................................68
8.33 Validity-Time AVP........................................69
8.34 Final-Unit-Indication AVP................................69
8.35 Final-Unit-Action AVP....................................70
8.36 Restriction-Filter-Rule AVP..............................71
8.37 Redirect-Server AVP......................................71
8.38 Redirect-Address-Type AVP................................71
8.39 Redirect-Server-Address AVP..............................72
8.40 Multiple-Services-Indicator AVP..........................72
8.41 Requested-Action AVP.....................................73
8.42 Service-Parameter-Info AVP...............................73
8.43 Service-Parameter-Type AVP...............................74
8.44 Service-Parameter-Value AVP..............................74
8.45 Subscription-Id AVP......................................74
8.46 Subscription-Id-Type AVP.................................75
8.47 Subscription-Id-Data AVP.................................75
8.48 User-Equipment-Info AVP..................................75
8.49 User-Equipment-Info-Type AVP.............................76
8.50 User-Equipment-Info-Value AVP............................76
9. Result Code AVP values........................................76
9.1 Transient Failures........................................77
9.2 Permanent Failures........................................77
10. AVP Occurrence Table.........................................77
10.1 Credit Control AVP Table.................................78
10.2 Re-Auth-Request/Answer AVP Table.........................79
11. RADIUS/Diameter Credit-control Interworking Model............79
12. IANA Considerations..........................................82
12.1 Application Identifier...................................82
12.2 Command Codes............................................82
12.3 AVP Codes................................................82
12.4 Result-Code AVP Values...................................82
12.5 CC-Request-Type AVP......................................83
12.6 CC-Session-Failover AVP..................................83
12.7 CC-Unit-Type AVP.........................................83
12.8 Check-Balance-Result AVP.................................83
12.9 Credit-Control AVP.......................................83
12.10 Credit-Control-Failure-Handling AVP.....................83
12.11 Direct-Debiting-Failure-Handling AVP....................83
12.12 Final-Unit-Action AVP...................................84
12.13 Multiple-Services-Indicator AVP.........................84
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12.14 Redirect-Address-Type AVP...............................84
12.15 Requested-Action AVP....................................84
12.16 Subscription-Id-Type AVP................................84
12.17 Tariff-Change-Usage AVP.................................84
12.18 User-Equipment-Info-Type AVP............................84
13. Credit-control Application Related Parameters................85
14. Security Consideration.......................................85
14.1 Direct Connection with Redirects.........................86
15. References...................................................87
15.1 Normative................................................87
15.2 Non-Normative............................................88
16. Acknowledgement..............................................89
Appendix A Credit Control sequences..............................89
A.1 Flow I...................................................89
A.2 Flow II..................................................91
A.3 Flow III.................................................93
A.4 Flow IV..................................................93
A.5 Flow V...................................................95
A.6 Flow VI..................................................96
A.7 Flow VII.................................................97
A.8 Flow VIII................................................98
A.9 Flow IX..................................................100
Author's Address................................................105
Intellectual Property Considerations............................106
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1. Introduction
This document specifies a DIAMETER application that can be used to
implement real-time credit-control for a variety of end user services
such as network access, Session Initiation Protocol (SIP) services,
messaging services, download services etc. It provides a general
solution to the real-time cost and credit control.
The prepaid model has been shown to be very successful for instance
in GSM networks where network operators offering prepaid services
have experienced a substantial growth of their customer base and
revenues. Prepaid services are now cropping up in many other wireless
and wire line based networks as well.
In next generation wireless networks, additional functionality is
required beyond that specified in the Diameter base protocol. For
example, the 3GPP Charging and Billing requirements [3GPPCHARG] state
that an application must be able to rate service information in real-
time. In addition, it is necessary to check that the end user's
account provides coverage for the requested service, prior to
initiation of that service. When an account is exhausted or expired,
the user must be denied the ability to compile additional chargeable
events.
A mechanism needs to be provided to allow the user to be informed of
the charges to be levied for a requested service. In addition, there
are services such as gaming and advertising that may credit as well
as debit from a user account.
The other Diameter applications provide service specific
authorization and they do not provide credit authorization for
prepaid users. The credit authorization shall be generic and
applicable to all the service environments required to support
prepaid services.
To fulfill these requirements, it is necessary to facilitate credit-
control communication between the network element providing the
service (e.g. Network Access Server, SIP Proxy, Application Server
etc.) and a credit-control server.
The scope of this specification is the credit authorization. Service
specific authorization and authentication is out of the scope.
1.1 Requirements language
In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL",
"RECOMMENDED", "SHOULD", and "SHOULD NOT", are to be interpreted as
described in [KEYWORDS].
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1.2 Terminology
AAA
Authentication, Authorization and Accounting
AA answer
AA answer generically refers to a service specific authorization and
authentication answer. AA answer commands are defined in service
specific authorization applications e.g. [NASREQ] and [DIAMMIP].
AA request
AA request generically refers to a service specific authorization and
authentication request. AA request commands are defined in service
specific authorization applications e.g. [NASREQ] and [DIAMMIP].
Credit-control
Credit-control is a mechanism, which directly interacts in real-time
with an account and controls or monitors the charges, related to the
service usage. Credit-control is a process of: checking if credit is
available, credit-reservation, deduction of credit from the end user
account when service is completed and refunding of reserved credit
not used.
Diameter Credit-control Server
Diameter Credit-control server acts as a prepaid server, performing
real-time rating and credit control. It is located in the home domain
and is accessed by service elements or Diameter AAA servers in real-
time for purpose of price determination and credit-control before the
service event is delivered to the end-user. It may also interact with
business support systems.
Diameter Credit-control Client
A Diameter credit-control client is an entity that interacts with a
credit-control server. It monitors the usage of the granted quota
according to instructions returned by credit-control server.
Interrogation
The Diameter credit-control client uses interrogation to initiate a
session based credit-control process and during the credit-control
process to report the used quota and request a new one. An
interrogation maps to a request/answer transaction.
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One-time event
Basically a request/answer transaction of type event.
Rating
The act of determining the cost of the service event.
Service
A type of task that is performed by a service element for an end
user.
Service Element
A network element that provides a service to the end users. The
Service Element may include the Credit-control Client, or another
entity (e.g. RADIUS AAA server) can act as a Credit-control Client on
behalf of the Service Element. In the latter case the interface
between the Service Element and the Diameter Credit-control Client is
outside the scope of this specification. Examples of the Service
Elements include Network Acess Server (NAS), SIP Proxy and
Application Servers such as messaging server, content server and
gaming server.
Service Event
An event relating to a service provided to the end user.
Session based credit-control
A credit-control process that makes use of several interrogations:
the first, possible intermediate and the final interrogation. The
first interrogation is used to reserve money from the user's account
and initiate the process. The intermediate interrogations may be
needed to request new quota while the service is being rendered. The
final interrogation is used to exit the process. The credit-control
server is required to maintain session state for session-based
credit-control.
1.3 Advertising application support
Diameter nodes conforming to this specification MUST advertise
support by including the value of 4 in the Auth-Application-Id of the
Capabilities-Exchange-Request and Capabilities-Exchange-Answer
command [DIAMBASE].
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2. Architecture Models
The current accounting models specified in the Radius Accounting
[RFC2866] and Diameter base [DIAMBASE] are not sufficient for real-
time credit control, where credit-worthiness is to be determined
prior to service initiation. Also, the existing Diameter
authorization applications [NASREQ] and [DIAMMIP] only provides
service authorization, but do not provide credit authorization for
prepaid users. In order to support real-time credit control a new
type of server is needed in the AAA infrastructure; Diameter credit-
control server. The Diameter credit-control server is the entity
responsible of credit authorization for prepaid subscribers.
A service element may authenticate and authorize the end user with
the AAA server using AAA protocols, e.g. RADIUS or a Diameter base
protocol with a possible Diameter application.
Accounting protocols such as RADIUS accounting and the Diameter base
accounting protocol can be used to provide accounting data to the
accounting server after service is initiated, and to provide possible
interim reports until service completion. However, for real-time
credit control, these authorization and accounting models are not
sufficient.
When real-time credit-control is required, the credit-control client
contacts the credit-control server with possible service event
information. The credit-control process is performed in order to
determine potential charges and to verify whether the end user's
account balance is sufficient to cover the cost of the service being
rendered.
Figure 1 illustrates the typical credit-control architecture, which
consist of a Service Element with embedded Diameter credit-control
client, a Diameter credit-control server and an AAA server. A
Business Support System is usually deployed; it includes at least the
billing functionality. The credit-control server and AAA server in
this architecture model are logical entities. The real configuration
can combine them into a single host. The credit-control protocol is
the Diameter base protocol with the Diameter credit-control
application.
When an end user requests services such as SIP services or messaging
services, the request is typically forwarded to a service element
(e.g. SIP Proxy) in the user's home domain. In some cases it might be
possible that the service element in the visited domain can offer
services to the end user, however a commercial agreement must exist
between the visited domain and the home domain. Network access is an
example of a service offered in the visited domain where the NAS,
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through an AAA infrastructure, authenticates and authorizes the user
with the user's home network.
Service Element AAA and CC
+----------+ +---------+ protocols+-----------+ +--------+
| End |<---->|+-------+|<------------>| AAA | |Business|
| User | +->|| CC || | Server |->|Support |
| | | || client||<-----+ | | |System |
+----------+ | |+-------+| | +-----------+ | |
| +---------+ | ^ +--------+
+----------+ | | CC protocol | ^
| End |<--+ | +-----v----+ |
| User | +------>|Credit- | |
+----------+ credit-control |control |--------+
protocol |server |
+----------+
Figure 1: Typical credit-control architecture
There can be multiple credit-control servers in the system for
reasons of redundancy and load balancing. The system can also contain
separate rating server(s) and accounts can be located in a
centralized database. For duplicate detection only one place in the
credit-control system should perform duplicate detection to ensure
that the end user's account is not debited or credited multiple times
for the same service event. System internal interfaces can exist to
relay messages between servers and an account manager. However the
detailed architecture of credit-control system and its interfaces are
implementation specific and are out of scope of this specification.
There can exist protocol transparent Diameter relays between credit-
control client and credit-control server. Also Diameter Redirect
agents, which refer credit control clients, to credit control servers
and allow them to communicate directly can exist. These agents
transparently support the Diameter credit-control application. The
different roles of Diameter Agents are defined in Diameter base
[DIAMBASE] section 2.8.
If Diameter credit-control proxies exist between the credit-control
client and the credit-control server, they MUST advertise the
Diameter credit-control application support.
3. Credit-Control Messages
This section defines new Diameter message Command-Code values that
MUST be supported by all Diameter implementations that conform to
this specification. The Command Codes are:
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Command-Name Abbrev. Code Reference
-----------------------------------------------------------
Credit-Control-Request CCR xxx 3.1
Credit-Control-Answer CCA xxx 3.2
[IANA please fill in xxx (suggested value 272) and remove this note]
Diameter Base [DIAMBASE] defines in the section 3.2 the Command Code
ABNF specification. These formats are observed in Credit-Control
messages.
3.1 Credit-Control-Request (CCR) Command
The Credit-Control-Request message (CCR), indicated by the command-
code field set to xxx [IANA please fill in xxx (suggested value 272)
and remove this note] and the 'R' bit set in the Command Flags field,
is used between the Diameter credit-control client and the credit-
control server to request credit authorization for a given service.
The Auth-Application-Id MUST be set to the value 4 indicating the
Diameter credit-control application.
Message Format
<Credit-Control-Request> ::= < Diameter Header: xxx, REQ, PXY >
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Application-Id }
{ CC-Request-Type }
{ CC-Request-Number }
[ Destination-Host ]
[ User-Name ]
[ CC-Sub-Session-Id ]
[ Acct-Multi-Session-Id ]
[ Origin-State-Id ]
[ Event-Timestamp ]
*[ Subscription-Id ]
[ Service-Identifier ]
[ Termination-Cause ]
[ Requested-Service-Unit ]
[ Requested-Action ]
*[ Used-Service-Unit ]
[ Multiple-Services-Indicator ]
*[ Multiple-Services-Credit-Control
]
*[ Service-Parameter-Info ]
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[ CC-Correlation-Id ]
[ User-Equipment-Info ]
*[ Proxy-Info ]
*[ Route-Record ]
*[ AVP ]
[IANA please fill in xxx (suggested value 272) and remove this note]
3.2 Credit-Control-Answer (CCA) Command
The Credit-Control-Answer message (CCA), indicated by the command-
code field set to xxx [IANA please fill in xxx (suggested value 272)
and remove this note] and the 'R' bit cleared in the Command Flags
field, is used between the credit-control server and the Diameter
credit-control client to acknowledge a Credit-Control-Request
command.
Message Format
<Credit-Control-Answer> ::= < Diameter Header: xxx, PXY >
< Session-Id >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
{ Auth-Application-Id }
{ CC-Request-Type }
{ CC-Request-Number }
[ User-Name ]
[ CC-Session-Failover ]
[ CC-Sub-Session-Id ]
[ Acct-Multi-Session-Id ]
[ Origin-State-Id ]
[ Event-Timestamp ]
*[ Subscription-Id ]
[ Granted-Service-Unit ]
*[ Multiple-Services-Credit-Control ]
[ Cost-Information]
[ Final-Unit-Indication ]
[ Check-Balance-Result ]
[ Credit-Control-Failure-Handling ]
[ Direct-Debiting-Failure-Handling ]
[ Validity-Time]
*[ Redirect-Host AVP ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
*[ Proxy-Info ]
*[ Route-Record ]
*[ AVP ]
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[IANA please fill in xxx (suggested value 272) and remove this note]
4. Credit Control Application Overview
The credit authorization process takes place before and during
service delivery to the end user and generally requires user's
authentication and authorization before any request is sent to the
credit-control server.
The credit control application defined in this specification supports
two different credit authorization models: credit authorization with
money reservation and credit authorization with direct debiting.
In both the models, the credit control client requests credit
authorization to the credit control server prior to allow any service
to be delivered to the end user.
In the first model, the credit control server rates the request,
reserves a suitable amount of money from the user's account and
returns the corresponding amount of credit resources. Note that
credit resources may not imply actual monetary credit; credit
resources may be granted to the credit control client in form of
units (e.g. data volume or time) to be metered.
Upon reception of a successful credit authorization answer with a
certain amount of credit resources, the credit control client allows
service delivery to the end user and starts monitoring the usage of
the granted resources. When the credit resources granted to the user
have been consumed, or the service has been successfully delivered or
terminated, the credit control client reports back to the server the
used amount. The credit control server deducts the used amount from
the end user's account; it may perform rating and make a new credit
reservation if the service delivery is continuing. This process is
accomplished with session based credit control that includes the
first interrogation, possible intermediate interrogations and the
final interrogation. For session based credit control, both the
credit control client and the credit control server are required to
maintain credit control session state.
In contrast, credit authorization with direct debiting is a single
transaction process where the credit control server directly deducts
a suitable amount of money from the user's account as soon as the
credit authorization request is received. Upon reception of a
successful credit authorization answer, the credit control client
allows service delivery to the end user. This process is accomplished
with the One-time event. Session state is not maintained.
In a multi-service environment, an end user may issue an additional
service request (e.g. data service) during an ongoing service (e.g.
voice call) towards the same account; or during an active multimedia
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session an additional media type is added to the session causing a
new simultaneous request towards same account. Consequently this
needs to be considered when credit resources are granted to the
services.
The credit control application also supports operations such as
service price enquiry, user's balance check and refund of credit on
the user's account. These operations are accomplished with the One-
time event. Session state is not maintained.
A flexible Credit control application specific failure handling is
defined where the home service provider can model the credit control
client behavior according to its own credit risk management policy.
The Credit-Control-Failure-Handling AVP and the Direct-Debiting-
Failure-Handling AVP are defined to determine what to do if the
sending of credit-control messages to the credit-control server has
been temporarily prevented. The usage of Credit-Control-Failure-
Handling AVP and the Direct-Debiting-Failure- Handling AVP gives
flexibility to have different failure handling for credit-control
session and one time event direct debiting.
4.1 Service-Specific Rating Input and Interoperability
The Diameter Credit Control Application defines the framework for
credit control; it provides generic credit control mechanisms
supporting multiple service applications. The Credit Control
Application, therefore, does not define AVPs that could be used as
input in the rating process. Listing the possible services that could
use this Diameter application is seen as out of scope for this
generic mechanism as well.
It is reasonable to expect that there will exist a service level
agreement between providers of the credit control client and the
credit control server covering the charging, services offered,
roaming agreements, agreed rating input, etc.
There are two ways for providing rating input to the credit control
server, either by using AVPs or by including them in the Service-
Parameter-Info AVP. The general principle for sending rating
parameters is that the service SHOULD re-use existing AVPs, if the
service can use AVPs defined in existing service specific Diameter
applications (e.g. NASREQ for network access services).
Alternatively, new AVPs can be defined if the existing AVPs do not
provide sufficient rating information. The Service-Parameter-Info AVP
MAY be used as a container to pass legacy rating information in its
original encoded form (e.g. ASN.1 BER). In that case the rating input
is embedded in the Service-Parameter-Info AVP as defined in section
8.42. New service applications SHOULD favor the use of explicitly
defined AVPs, to simplify interoperability.
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The service specific rating input AVPs, the contents of the Service-
Parameter-Info AVP or Service-Identifier AVP are not within the scope
of this document. To facilitate interoperability, it is RECOMMENDED
that the rating input and values of service identifiers are
coordinated via an informational RFC or other permanent and readily
available reference such as the specification of another cooperative
standardization body (e.g. 3GPP, OMA and 3GPP2) SHOULD be used.
However, private services may be deployed that are subject to
agreements between providers of the credit control server and client,
in this case vendor specific AVPs can be used.
This specification, together with service specific documents, is
governing the credit control message. The rule is that service
specific documents only define what existing AVPs or new AVPs are
used as input to the rating process (i.e. they do not define new
credit control applications), and thus need to be included in the
Credit-Control-Request command by a Diameter Credit Control Client
supporting a given service as *[AVP]. In order to define new AVPs,
service specific documents MUST follow the practices defined in
[DIAMBASE]. The service SHOULD be identified using the Service-
Identifier AVP. The Service-Identifier AVP MUST be a unique
identifier for a given service as defined in section 8.28.
As a result it is the combination of support of the Diameter Credit
Control Application and the service defined in the Service-Identifier
AVP, which defines interoperability between any given credit control
client and server.
Diameter credit control implementations are required to support the
Mandatory rating AVPs defined in service specific documentation of
the services they support. Introducing new credit control mechanisms
not defined in this specification implies the definition of a new
version of the Diameter Credit Control Application and corresponding
Application Identifier.
When service specific documents include RADIUS vendor specific
attributes that could be used as input in the rating process, the
rules described in [NASREQ] for formatting the Diameter AVP MUST be
followed. For example, the AVP code used is the vendor attribute type
code, the Vendor-Specific flag MUST be set to 1 and the Vendor-ID
MUST be set to the IANA Vendor identification value. The Diameter AVP
data field contains only the attribute value of the RADIUS attribute.
In case a rating input required for the rating process is incorrect
in the Credit control request, or the credit control server does not
support the requested service, the Credit control answer MUST contain
error code DIAMETER_RATING_FAILED. A CCR message with this error MUST
contain one or more Failed-AVP AVPs containing the missing and/or
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unsupported AVPs that caused the failure. A Diameter credit control
client receiving error code DIAMETER_RATING_FAILED in answer to a
request MUST NOT send such similar requests in the future.
5. Session Based Credit-control
5.1 General Principles
For a session-based credit-control, several interrogations are
needed: the first, intermediate (optional) and the final
interrogation. This is illustrated in Figure 2 and Figure 3.
If the credit-control client performs credit-reservation before
granting service to the end user it MUST use several interrogations
towards the credit-control server (i.e. session based credit-
control). In this case the credit-control server MUST maintain the
credit control session state.
Each credit-control session MUST have globally unique Session-Id as
defined in [DIAMBASE] and it MUST NOT be changed during the lifetime
of a credit-control session.
There are certain applications that require multiple credit control
sub-sessions. Such applications would send messages with a constant
Session-Id AVP, but a different CC-Sub-Session-Id AVP. If several
credit sub-sessions will be used, all sub-sessions MUST be closed
separately before closing the main session to be able to report used
units per sub-session. The absence of this AVP implies no sub-
sessions are in use.
It should be noted that the service element might send a service
specific re-authorization message to the AAA server due to expiration
of the authorization-lifetime during an ongoing credit control
session. However, the service specific re-authorization does not
influence the credit authorization that is ongoing between credit-
control client and credit-control server since credit authorization
is controlled by the burning rate of the granted quota.
In the event that service specific re-authorization fails the user
will be disconnected and the credit-control client MUST send a final
interrogation to the credit-control server.
The Diameter credit-control server may want to control the validity
time of the granted quota and/or the production of intermediate
interrogations, thus it MAY include the Validity-Time AVP in the
answer message to the credit-control client. Upon expiration of the
Validity-Time, the credit-control client MUST generate a credit-
control update request and report the used quota to the credit-
control server. It is up to the credit-control server to determine,
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the value of the Validity-Time to be used for consumption of the
granted service units. If the Validity-Time is used, its value SHOULD
be given as input to set the session supervision timer Tcc (the
session supervision timer MAY be set to two times the value of the
Validity-Time as defined in section 13). Since credit-control update
requests are also produced at the expiry of granted service units
and/or for mid-session service events the omission of Validity-Time
does not mean that intermediate interrogation for the purpose of
credit control are not performed.
The Diameter credit-control server and client MAY optionally support
a tariff change mechanism. The Diameter credit-control server may
include a Tariff-Time-Change AVP in the answer message. Note that the
granted units should be allocated based on the worst-case scenario in
case of forthcoming tariff change, so that the overall reported used
units would never exceed the credit reservation.
When the Diameter credit-control client reports the used units and a
tariff change has occurred during the reporting period then the
Diameter credit-control client MUST separately itemize the units used
before and after the tariff change. In case the client is unable to
distinguish whether units that straddle the tariff change are used
before or after the tariff change, the credit-control client MUST
itemize those units in a third category.
If a client does not support the tariff change mechanism, and it
receives a CCA message carrying the Tariff-Time-Change AVP, it MUST
terminate the credit control session, giving a reason of
DIAMETER_BAD_ANSWER in the Termination-Cause AVP.
For time based services the quota is continuously consumed at the
regular rate of 60 seconds per minute, the server already knows at
the time when credit resources are allocated how many units will be
consumed before the tariff time change and how many units will be
consumed after. Similarly, the server can determine the units
consumed at the before rate and the units consumed at the rate
afterwards in the event that the end-user closes the session before
the consumption of the allotted quota. There is no need for
additional traffic between client and server in case of tariff time
changes for continuous time based service, therefore the tariff
change mechanism is not used for continuous time based services. For
time-based services where the quota is NOT continuously consumed at a
regular rate, the tariff change mechanism described for volume and
event units MAY be used.
5.1.1 Credit-Control for Multiple Services within a (sub-)Session
When multiple services are used within one user session and each
service or group of services are subject to different cost, it is
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necessary to perform credit-control for each of these services
independently. Making use of credit control sub-sessions to achieve
independent credit-control will result in increased signaling load
and resources usage in both the credit control client and the credit
control server. For instance, during one network access session the
end user may use several http-services subject to different access
cost, the network access specific attributes such as the quality of
service (QoS) are common to all the services carried within the
access bearer, but the cost of the bearer may vary depending on its
content.
To optimally support these scenarios, the credit control application
enables for independent credit control of multiple services in a
single credit control (sub-)session. This is achieved by including
the optional Multiple-Services-Credit-Control AVP in Credit-Control-
Request/Answer messages. It is possible to request and allocate
resources as a credit pool that is shared between multiple services.
The services can be further grouped into rating groups in order to
achieve even further aggregation of credit allocation. It is also
possible to request and allocate quotas on a per service basis. Where
quotas are allocated to a pool by means of the Multiple-Services-
Credit-Control AVP, the quotas remain independent objects that can be
re-authorized independently at any time. Quotas can also be given
independent result codes, validity times and Final-Unit-Indications.
A Rating-group groups a set of services, identified by a Service-
Identifier, subject to the same cost and rating type (e.g.
$0.1/minute). It is assumed that the service element is provided, by
means outside the scope of this specification, with Rating-Groups,
with Service-Identifiers and their associated parameters that define
what need to be metered (example of parameters associated to Service-
Identifiers are IP 5-tuple, HTTP URL etc.). Service-identifiers
enable on a per-service based credit authorization as well as
itemized reporting of service usage. It is up to the credit control
server whether to authorize credit for one or more services or for
the whole rating-group, but the client SHOULD always report used
units itemizing the service level usage. Where quota is allocated to
a rating-group, all the services belonging to that rating-group draw
from the allotted quota. The following is a graphical representation
of the relation between service-identifiers, rating-groups, credit
pools and credit-control (sub-)session.
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DCC (Sub-)Session
|
+------------+-----------+-------------+--------------- +
| | | | |
Service-Id a Service-Id b Service-Id c Service-Id d.....Service-Id z
| \ / \ / /
| \ / \ / /
| Rating-Group 1 Rating-Group 2.......Rating-Group n
| | |
Quota- ---------------Quota Quota
\ / |
\ / |
Credit-Pool Credit-Pool
In case independent credit control of multiple services is used, the
validity-time and final-unit-indication SHOULD be present either in
the Multiple-Service-Credit-Control AVP(s) or at command level as
single AVPs. However, the Result-Code AVP MAY be present both on the
command level and within the Multiple-Services-Credit-Control AVP. If
the Result-Code on the command level indicates other value than
SUCCESS then the Result-Code on command level takes precedence over
the one(s) included in the Multiple-Services-Credit-Control AVP.
The Credit-control client MUST indicate support for independent
credit control of multiple services within a (sub-)session by
including the Multiple-Services-Indicator AVP in the first
interrogation. A Credit-Control-server not supporting the feature
MUST treat the Multiple-Services-Indicator AVP and possibly received
Multiple-Services-Credit-Control AVPs as invalid AVPs.
If the client indicated support for independent credit control of
multiple services, a credit-control server that whishes to use the
feature MUST return the granted units within the Multiple-Services-
Credit-Control AVP associated to the corresponding service-identifier
and/or rating-group.
To avoid credit fragmentation and unnecessary load on the credit
control server, it is possible for service units to be provided to
multiple services or rating groups as a pool. This is achieved by
providing the service units in the form of a quota for a particular
service or rating group in the Multiple-Services-Credit-Control AVP,
but also including a reference to a credit pool for that unit type.
The reference includes a multiplier derived from the rating
parameter, which translates from service units of a specific type to
the abstract service units in the pool. For instance if the rating
parameter for service 1 is $1/MB and rating parameter for service 2
is $0.5/MB the multipliers could be 10 and 5 for service 1 and
service 2 respectively.
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If M is the total service units within the pool, M1, M2, ... , Mn are
the multipliers provided for services 1, 2, ..., n and C1, C2,... ,Cn
are the used resources within the session, then the pool credit is
exhausted and re-authorization MUST be sought when:
C1*M1 + C2*M2 + ... + Cn*Mn >= M
The total credit in the pool, M, is calculated from the quotas which
are currently allocated to the pool as follows:
M = Q1*M1 + Q2*M2 + ... + Qn*Mn
If services or rating groups are added to or removed from the pool,
then the total credit is adjusted appropriately. Note that when the
total credit is adjusted because services or rating groups are
removed from the pool, the value that need to be removed is the
consumed one (i.e. Cx*Mx).
Re-authorizations for an individual service or rating group may be
sought at any time, for example if a 'non-pooled' quota is used up or
the Validity-Time expires.
Where multiple G-S-U-Pool-Reference AVPs (section 8.30) with the same
G-S-U-Pool-Identifier are provided within a Multiple-Services-Credit-
Control AVP (section 8.16) together with the Granted-Service-Unit
AVP, then these MUST have different CC-Unit-Type values and they all
draw on the credit pool separately. For instance, if one multiplier
for time (M1t) and one multiplier for volume (M1v) are given, then
the used resources from the pool is the sum C1t*M1t + C1v*M1v, where
C1t are the time units and C1v are the volume unit.
Where service units are provided within a Multiple-Services-Credit-
Control AVP without a corresponding G-S-U-Reference AVP then these
are handled independently from any credit pool and from any other
services or rating groups within the session.
The credit pool concept is an optimal tool to avoid the over-
reservation effect of the basic single quota tariff time change
mechanism (the mechanism described in section 5.1). Therefore,
Diameter credit-control clients and servers implementing the
independent credit control of multiple services SHOULD leverage the
credit pool concept when supporting the tariff time change. The
Diameter credit-control server SHOULD include both the Tariff-Time-
Change and Tariff-Change-Usage AVPs in two quota allocations in the
answer message (i.e. two instances of the Multiple-Services-Credit-
Control AVP). One of the granted units is allocated to be used before
the potential tariff change while the second granted units are used
after a tariff change. Both granted unit quotas MUST contain the same
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Service-Identifier and/or Rating-Group. This dual quota mechanism
ensures that the overall reported used units would never exceed the
credit reservation. The Diameter credit-control client reports both
the used units before and after the tariff change in a single
instance of the Multiple-Services-Credit-Control AVP.
The failure handling for credit control sessions is defined in
section 5.7 and reflected in the basic credit-control state machine
in section 7 Credit-control clients and servers implementing the
independent credit control of multiple services in a (sub-)session
functionality MUST ensure failure handling and general behavior fully
consistent with the above mentioned sections while capable of
handling parallel ongoing credit re-authorization within a (sub-
)session. It is then RECOMMENDED that Diameter credit-control clients
maintain a PENDING-U message queue and restarts the Tx timer (section
13) every time a CCR message with value UPDATE_REQUEST is sent while
in PENDING-U state. When answers to all the pending messages are
received the state machine moves to OPEN and Tx is stopped. Naturally
the action performed when a problem is detected for the session
according to section 5.7, affect all the ongoing services (e.g.
failover to a backup server if possible affect all the CCR messages
with value UPDATE_REQUEST in the PENDING-U queue).
Since the client may send CCR messages with value UPDATE_REQUEST
while in PENDING-U (i.e. without waiting for an answer to ongoing
credit re-authorization), the time space between these requests may
be very short and the server may not have received the previous
request(s) yet. Therefore in this situation the server may receive
out of sequence requests and SHOULD NOT consider this as an error
condition, a proper answer is to be returned to each of those
requests.
5.2 First Interrogation
When session based credit-control is required (e.g. the
authentication server indicated prepaid user), the first
interrogation MUST be sent before the Diameter credit-control client
allows any service event to the end user. The CC-Request-Type is set
to the value INITIAL_REQUEST in the request message.
If the Diameter credit-control client knows the cost of the service
event (e.g. a content server delivering ringing tones may know their
cost) the monetary amount to be charged is included in the Requested-
Service-Unit AVP. If the Diameter credit-control client does not know
the cost of the service event, the Requested-Service-Unit AVP MAY
contain the number of requested service events. Where the Multiple-
Services-Credit-Control AVP is used, it MUST contain the Requested-
Service-Unit AVP to indicate that quota for the associated
service/rating-group is requested. The Service-Identifier AVP, in
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case of multiple services the Service-Identifier AVP or the Rating-
Group AVP within the Multiple-Services-Credit-Control AVP, always
indicates the concerned service. Additional service event
information to be rated MAY be sent as service specific AVPs or MAY
be sent within the Service-Parameter-Info AVP at command level.
The Event-Timestamp AVP contains the time when the service event is
requested in the service element. The Subscription-Id AVP SHOULD be
included to identify the End-User in the credit-control server. The
credit control client MAY include the User-Equipment-Info AVP so that
the credit control server has some indication about the type and
capabilities of the end user access device. How the credit control
server uses this information is outside the scope of this document.
The credit-control server SHOULD rate the service event and make a
credit-reservation from the end user's account that covers the cost
of the service event. If the type of the Requested-Service-Unit AVP
is money, no rating is needed but the corresponding monetary amount
is reserved from end user's account.
The credit-control server returns the Granted-Service-Unit AVP in the
Answer message to the Diameter credit-control client. The Granted-
Service-Unit AVP contains the amount of service units that the
Diameter credit-control client can provide to the end user until a
new Credit-Control-Request MUST be sent to the credit-control server.
If several unit types are sent in the Answer message the credit-
control client MUST handle each unit type separately. The type of the
Granted-Service-Unit AVP can be time, volume, service specific or
money depending on the type of service event. The unit type(s) SHOULD
NOT be changed within an ongoing credit-control session.
There MUST be maximum one instance of the same unit type in one
Answer message. However, in case multiple quotas are conveyed to the
credit control client in the Multiple-Services-Credit-Control AVPs,
it is possible to carry two instances of the same unit type
associated to a service-identifier/rating-group. This is typically
the case when a tariff time change is expected and the credit-control
server wants to make a distinction between the granted quota before
and after tariff change.
If the credit-control server determines that no further control is
needed for the service it MAY include the result code indicating that
the credit-control is not applicable (e.g. service is free of
charge). This result code at command level implies that the credit-
control session is to be terminated.
The Credit-Control-Answer message MAY also include the Final-Unit-
Indication AVP to indicate that the answer message contains the final
units for the service. After the end user has consumed these units,
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the Diameter credit-control-client MUST behave as described in
section 5.6.
This document defines two different approaches to perform the first
interrogation to be used indifferent network architectures. The first
approach uses credit-control messages after user's authorization and
authentication took place. The second approach uses service specific
authorization messages to perform the first interrogation during the
user's authorization/authentication phase, and credit-control
messages for the intermediate and the final interrogations. In case
an implementation of the credit-control client supports both the
methods, it SHOULD be configurable what method to use.
In service environments such as the Network Access Server (NAS), it
is desired to perform the first interrogation as part of the
authorization/authentication process for the sake of protocol
efficiency. Further credit authorizations after the first
interrogation took place are performed with credit control commands
defined in this specification. Implementations of credit-control
client operating in the mentioned environments SHOULD support this
method. In case the credit-control server and AAA server are separate
physical entities the service element sends the request messages to
the AAA server, which then issue an appropriate request or proxy the
received request forward to the credit-control server.
In other service environments, such as the 3GPP network and some SIP
scenario, there is a substantial decoupling between
registration/access to the network and the actual service request
(i.e. the authentication/authorization is executed once at
registration/access to the network and is not executed for every
service event requested by the subscriber). In such environments it
is more appropriate to perform the first interrogation after the user
has been authenticated and authorized. The first interrogation, the
intermediate and final interrogations are executed with credit
control commands defined in this specification.
Other IETF standards or standards developed by other standardization
bodies may define what is the most suitable method in their
architecture.
5.2.1 First Interrogation after Authorization and Authentication
The Diameter credit-control client in the service element may get
information from the authorization server whether credit-control is
required based on its knowledge of the end user. If credit-control is
required the credit-control server needs to be contacted prior to
initiating service delivery to the end user. The accounting protocol
and the credit-control protocol can be used in parallel, the
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authorization server may also drive whether the parallel accounting
stream is required.
The following diagram illustrates the case where both protocols are
used in parallel and the service element sends credit-control
messages directly to the credit-control server. More credit-control
sequence examples are given in Annex A.
Diameter
End-User Service Element AAA Server CC Server
(CC Client)
| Registration | AA request/answer(accounting,cc or both)|
|<----------------->|<------------------>| |
| : | | |
| : | | |
| Service Request | | |
|------------------>| | |
| | CCR(Initial,Credit-Control AVPs) |
| +|---------------------------------------->|
| CC stream|| | CCA(Granted-Units)|
| +|<----------------------------------------|
| Service Delivery | | |
|<----------------->| ACR(start,Accounting AVPs) |
| : |------------------->|+ |
| : | ACA || Accounting stream |
| |<-------------------|+ |
| : | | |
| : | | |
| | CCR(Update,Used-Units) |
| |---------------------------------------->|
| | | CCA(Granted-Units)|
| |<----------------------------------------|
| : | | |
| : | | |
| End of Service | | |
|------------------>| CCR(Termination, Used-Units) |
| |---------------------------------------->|
| | | CCA |
| |<----------------------------------------|
| | ACR(stop) | |
| |------------------->| |
| | ACA | |
| |<-------------------| |
Figure 2: Protocol example with first interrogation after user's
authorization/authentication
5.2.2 Authorization Messages for First Interrogation
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The Diameter credit-control client in the service element MUST
actively co-operate with the authorization/authentication client in
the construction of the AA request by adding appropriate credit
control AVPs. The credit-control client MUST add the Credit-Control
AVP to indicate credit-control capabilities and MAY add other
relevant credit-control specific AVPs to the proper
authorization/authentication command to perform the first
interrogation towards the home Diameter AAA server. The Auth-
Application-Id is set to the appropriate value as defined in the
relevant service specific authorization/authentication application
document (e.g. [NASREQ], [DIAMMIP]). The home Diameter AAA server
authenticates/authorizes the subscriber and determines whether or not
credit-control is required.
If credit-control is not required for the subscriber the home
Diameter AAA server will respond as usual with an appropriate AA
answer message. If credit-control is required for the subscriber and
the Credit-Control AVP with the value set to CREDIT_AUTHORIZATION was
present in the authorization request, the home AAA server MUST
contact the credit-control server to perform the first interrogation.
If credit-control is required for the subscriber and the Credit-
Control AVP was not present in the authorization request, the home
AAA server MUST send an authorization reject answer message.
The Diameter AAA server supporting credit-control is required to send
the Credit-Control-Request command (CCR) defined in this document to
the credit-control server. The Diameter AAA server populates the CCR
based on service specific AVPs used for input to the rating process
and possibly credit-control AVPs received in the AA request. The
credit-control server will make money reservation from the user's
account, will rate the request and will send a credit-control answer
message to the home Diameter AAA server. The answer message includes
the Granted-Service-Unit AVP(s) and MAY include other credit-control
specific AVPs as appropriate. Additionally, the credit-control server
MAY set the Validity-Time and MAY include the Credit-Control-Failure-
Handling AVP and the Direct-Debiting-Failure-Handling AVP to
determine what to do if the sending of credit-control messages to the
credit-control server has been temporarily prevented.
Upon receiving the credit-control answer message from the credit-
control server, the home Diameter AAA server will populate the AA
answer with the received credit-control AVPs and with usual service
attributes according to the authorization/authentication specific
application (e.g. [NASREQ], [DIAMMIP]) and forward the packet to the
credit-control client. If the home Diameter AAA server receives a
credit-control reject message, it will simply generate an appropriate
authorization reject message to the credit-control client including
the credit-control specific error code.
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The credit-control client in this model sends further credit-control
messages to the credit-control server via the home Diameter AAA
server. Upon receiving successful authorization answer message with
the Granted-Service-Unit AVP(s), the credit-control client will grant
the service to the end user and will generate intermediate credit-
control request as required by using Credit-Control commands. The CC-
Request-Number of the first UPDATE_REQUEST MUST be set to 1 (for how
to produce unique value for the CC-Request-Number AVP see section
8.2).
If service specific re-authorization is performed (i.e.
authorization-lifetime expires), the credit-control client MUST add
to the service specific re-authorization request the Credit-Control
AVP with value set to RE-AUTHORIZATION to indicate that the credit-
control server MUST NOT be contacted. When session based credit-
control is used for the subscriber a constant Credit-Control messages
stream is flowing through the home Diameter AAA server. The home
Diameter AAA server can make use of this credit-control messages flow
to deduce that user's activity is ongoing; hence it is recommended to
set the authorization-lifetime to a reasonably high value when
credit-control is used for the subscriber.
In this scenario the home Diameter AAA server MUST advertise support
for the credit-control application to its peers during the capability
exchange process.
The following diagram illustrates the use of authorization /
authentication messages to perform the first interrogation. The
parallel accounting stream is not shown in the figure.
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Diameter
End-User Service Element AAA Server CC Server
(CC Client)
| Service Request | AA Request (CC AVPs) |
|------------------>|------------------->| |
| | | CCR(Initial, CC AVPs)
| | |------------------->|
| | | CCA(Granted-Units)
| | |<-------------------|
| | AA Answer(Granted-Units) |
| Service Delivery |<-------------------| |
|<----------------->| | |
| : | | |
| : | | |
| : | | |
| | | |
| | CCR(Update,Used-Units) |
| |------------------->| CCR(Update,Used-Units)
| | |------------------->|
| | | CCA(Granted-Units)|
| | CCA(Granted-Units)|<-------------------|
| |<-------------------| |
| : | | |
| : | | |
| End of Service | | |
|------------------>| CCR(Termination,Used-Units) |
| |------------------->| CCR(Term.,Used-Units)
| | |------------------->|
| | | CCA |
| | CCA |<-------------------|
| |<-------------------| |
Figure 3: Protocol example with use of the
authorization messages for the first interrogation.
5.3 Intermediate Interrogation
When all of the granted service units for one unit type are spent by
the end user or the Validity-Time is expired, the Diameter credit-
control client MUST send a new Credit-Control-Request to the credit-
control server. In the event that credit control for multiple
services in one credit control session is applied (i.e. units are
granted associated to Service-Identifier(s) or Rating-Group), a new
Credit-Control-Request MUST be sent to the credit-control server when
the whole credit reservation has been consumed, or upon expiration of
the Validity-Time. In the case when the Validity-Time is used, it is
always up to the Diameter credit-control client to send a new request
well in advance before the expiration of the previous request in
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order to avoiding interruption in the service element. Even if the
granted service units reserved by the credit-control server have not
been spent upon expiration of the Validity-Time, the Diameter credit-
control client MUST send a new Credit-Control-Request to the credit-
control server.
There can be also mid-session service events, which might affect the
rating of the current service events. In this case a spontaneous
updating (a new Credit-Control-Request) SHOULD be sent including
information related to the service event even if all the granted
service units have not been spent or the Validity-Time has not
expired.
When the used units are reported to the credit-control server, the
credit-control client will not have any units in its possession
before new granted units are received from the credit-control server.
When the new granted units are received from the credit-control
server these units apply from the point where the measurement of the
reported used units stopped. Where independent credit-control of
multiple services is supported, this process may be executed for one
or more services, a single rating-group or for a pool within the
(sub)session.
The CC-Request-Type AVP is set to the value UPDATE_REQUEST in the
intermediate request message. The Subscription-Id AVP SHOULD be
included in the intermediate message to identify the end user in the
credit-control server.
The Requested-Service-Unit AVP MAY contain the new amount of
requested service units. Where the Multiple-Services-Credit-Control
AVP is used, it MUST contain the Requested-Service-Unit AVP if new
quota for the associated service/rating-group is requested. The Used-
Service-Unit AVP contains the amount of used service units measured
from the point when the service became active or, in case of interim
interrogations are used during the session, from the point when the
previous measurement ended. The same unit types that are used in the
previous message SHOULD be used. If several unit types were included
in the previous answer message the used service units for each unit
type MUST be reported.
The Event-Timestamp AVP contains the time of the event that triggered
the sending of the new Credit-Control-Request.
The credit-control server MUST deduct the used amount from the end
user's account. It MAY rate the new request and make a new credit-
reservation from the end user's account that covers the cost of the
requested service event.
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The Credit-Control-Answer message with the CC-Request-Type AVP set to
the value UPDATE_REQUEST MAY include the Cost-Information AVP
containing the accumulated cost estimation for the session without
taking any credit-reservation into account.
The Credit-Control-Answer message MAY also include the Final-Unit-
Indication AVP to indicate that the answer message contains the final
units for the service. After the end user has consumed these units,
the Diameter credit-control-client MUST behave as described in
section 5.6.
There can be several intermediate interrogations within a session.
5.4 Final Interrogation
When the end user terminates the service session or according to the
graceful service termination as described in section 5.6, the
Diameter credit-control client MUST send a final Credit-Control-
Request message to the credit-control server. The CC-Request-Type AVP
is set to the value TERMINATION_REQUEST.
The Event-Timestamp AVP MAY contain the time of the session was
terminated.
The Used-Service-Unit AVP contains the amount of used service units
measured from the point when the service became active or, in case of
interim interrogations are used during the session, from the point
when the previous measurement ended. If several unit types were
included in the previous answer message the used service units for
each unit type MUST be reported.
After final interrogation the credit-control server MUST refund the
reserved credit amount not used to the end user's account and deduct
the used monetary amount from the end user's account.
The Credit-Control-Answer message with the CC-Request-Type set to the
value TERMINATION_REQUEST MAY include the Cost-Information AVP
containing the estimated total cost for the session in question.
If the user logoff during an ongoing credit-control session or some
other reason causes the user to be logged-off (e.g. final-unit
indication causes user logoff according to local policy) the service
element, according to application specific policy, may send a
session-termination-request (STR) to the home Diameter AAA server as
usual [DIAMBASE]. Figure 4 illustrates the case when the final-unit
indication causes the user logoff upon consumption of the final
granted units and STR is generated.
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End-User Service Element AAA Server CC Server
(CC Client)
| Service Delivery | | |
|<----------------->| | |
| : | | |
| : | | |
| : | | |
| | | |
| | CCR(Update,Used-Units) |
| |------------------->| CCR(Update,Used-Units)
| | |------------------->|
| | CCA(Final-Unit, Terminate)
| CCA(Final-Unit, Terminate)|<-------------------|
| |<-------------------| |
| : | | |
| : | | |
| Disconnect user | | |
|<------------------| CCR(Termination,Used-Units) |
| |------------------->| CCR(Term.,Used-Units)
| | |------------------->|
| | | CCA |
| | CCA |<-------------------|
| |<-------------------| |
| | STR | |
| |------------------->| |
| | STA | |
| |<-------------------| |
Figure 4: User disconnected due to account exhausted
5.5 Server-Initiated Credit Re-Authorization
The Diameter Credit Control Application supports server-initiated re-
authorization. The credit control server MAY optionally initiate the
credit re-authorization by issuing a Re-Auth-Request (RAR) as defined
in the Diameter base protocol [DIAMBASE]. The Auth-Application-Id in
the RAR message is set to 4 to indicate the Diameter Credit Control
Application and the Re-Auth-Request-Type is set to AUTHORIZE_ONLY.
Section 5.1.1 defines the feature to enable credit-control for
multiple services within a single (sub-)session where the server can
authorize credit usage at a different level of granularity. Further,
the server may provide credit resources to multiple services or
rating groups as a pool (see section 5.1.1 for details and
definitions). Therefore the server, based on its service logic and
its knowledge of the ongoing session, can decide to request credit
re-authorization for: a whole (sub-)session, a single credit pool, a
single service or a single rating-group. To request credit re-
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authorization for a credit pool, the server includes in the RAR
message the G-S-U-Pool-Identifier AVP indicating the affected pool.
To request credit re-authorization for a service or a rating-group,
the server includes in the RAR message the Service-Identifier AVP or
the Rating-Group AVP respectively. To request credit re-authorization
for all the ongoing services within the (sub-)session the server
includes none of the above mentione AVPs in the RAR message.
If a credit re-authorization is not already ongoing (i.e. the credit
control session is in OPEN state), a credit control client that
receives such a RAR message with Session-Id equal to a currently
active credit control session acknowledges the request by sending the
Re-Auth-Answer (RAA) message and MUST initiate the credit re-
authorization towards the server by sending a Credit-Control-Request
message with the CC-Request-Type AVP set to the value UPDATE_REQUEST.
The Result-Code 2002 (DIAMETER_LIMITED_SUCCESS) SHOULD be used in the
RAA message to indicate an additional message (i.e. CCR message with
value UPDATE_REQUEST) is required to complete the procedure. If a
quota was allocated to the service, the credit control client MUST
report the used quota in the Credit-Control-Request. Note that the
end user does not need to be prompted for the credit re-
authorization, since the credit re-authorization is transparent to
the user (i.e it takes place exclusively between the credit control
client and the credit control server).
Where multiple services in a user's session are supported, the
procedure of the above paragraph will be executed at the granularity
as requested by the server in the RAR message.
If credit re-authorization is ongoing at the time when the RAR
message is received (i.e. RAR-CCR collision), the credit control
client successfully acknowledges the request but it does not initiate
a new credit re-authorization. The Result-Code 2001
(DIAMETER_SUCCESS) SHOULD be used in the RAA message to indicate a
credit re-authorization procedure is already ongoing (i.e. the client
was in PendingU state when the RAR was received). The credit control
server SHOULD process the Credit-Control-Request as if it was
received in answer to the server initiated credit re-authorization,
and should consider the server initiated credit re-authorization
process successful upon reception of the Re-Auth-Answer message.
Where multiple services in a user's session are supported, it may
happen that the server requests credit re-authorization for a credit
pool (or for the (sub-)session) and a credit re-authorization is
already ongoing for some of the services or rating-groups. In this
case the client acknowledges the server request with a RAA message
and MUST send a new Credit-Control-Request message to perform re-
authorization for the remaining services/rating-groups. The Result-
Code 2002 (DIAMETER_LIMITED_SUCCESS) SHOULD be used in the RAA
message to indicate an additional message (i.e. CCR message with
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value UPDATE_REQUEST) is required to complete the procedure. The
server processes the received requests and returns an appropriate
answer to both of the requests.
The above-defined procedures are enabled for each of the possibly
active Diameter credit-control sub-sessions. The server MAY request
re-authorization for an active sub-session by including the CC-Sub-
Session-Id AVP in the RAR message in addition to the Session-Id AVP.
5.6 Graceful Service Termination
When the user's account runs out of money the user may be denied to
compile additional chargeable events. However, the home service
provider may offer some services, for instance access to a service
portal where it is possible to refill the account, for which the user
is allowed to benefit for a limited amount of time. This time is
usually dependant on the home service provider policy.
This section defines the graceful service termination optional
feature that MAY be supported by the credit control server. Credit
control client implementations MUST support the Final-Unit-Indication
with at least the tear down of the ongoing service session upon the
subscriber has consumed all the final granted units.
Where independent credit control of multiple services in a single
credit control (sub-)session is supported, it is possible to use the
graceful service termination for each of the services/rating-groups
independently. Naturally, the graceful service termination process
defined in the following sub-sections will apply to the specific
service/rating-group as requested by the server.
In some service environments (e.g. NAS) the graceful service
termination may be used to redirect the subscriber to a service
portal for online balance refill or other services offered by the
home service provider. In this case the graceful termination process
installs a set of packet filters to restrict the user's access
capability only to/from the specified destinations, all the IP
packets not matching the filters will be dropped or possibly re-
directed to the service portal. The user may also be displayed an
appropriate notification why the access has been limited. These
actions may be communicated explicitly from the server to client or
may be configured per-service at the client. Explicitly signaled
redirect or restrict instructions always take precedence over
configured ones.
It is also possible use the graceful service termination to connect
the prepaid user to a top-up server that play an announcement and
prompt the user to replenish the account. In such a case the credit
control server sends only the address of the top-up server where the
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prepaid user shall be connected after the final granted units have
been consumed. An example of this is given in Appendix A (Flow VII).
The credit control server MAY initiate the graceful service
termination by including the Final-Unit-Indication AVP in the Credit
Control Answer to indicate that the message contains the final units
for the service.
When the credit control client receives the Final-Unit-Indication AVP
in the answer from the server its behavior depends on the value
indicated in the Final-Unit-Action AVP. The server may request the
following actions: TERMINATE, REDIRECT and RESTRICT_ACCESS.
The following Figure illustrates the graceful service termination
procedure described in the following sub-sections.
Diameter
End-User Service Element AAA Server CC Server
(CC Client)
| Service Delivery | | |
|<----------------->| | |
| |CCR(Update,Used-Units) |
| |------------------->|CCR(Update,Used-Units)
| : | |------------------->|
| : | |CCA(Final-Unit,Action)
| : | |<-------------------|
| |CCA(Final-Unit,Action) |
| |<-------------------| |
| | | |
| : | | |
| : | | |
| : | | |
| /////////////// |CCR(Update,Used-Units) |
|/Final Units End/->|------------------->|CCR(Update,Used-Units)
|/Action and // | |------------------->|
|/Restrictions // | | CCA(Validity-Time)|
|/Start // | CCA(Validity-Time)|<-------------------|
| ///////////// |<-------------------| |
| : | | |
| : | | |
| Replenish Account +-------+ |
|<-------------------------------------------->|Account| |
| | | +-------+ |
| | | RAR |
| + | RAR |<===================|
| | |<===================| |
| | | RAA | |
| ///////////// | |===================>| RAA |
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| /If supported / | | CCR(Update) |===================>|
| /by CC Server/ | |===================>| CCR(Update) |
| ///////////// | | |===================>|
| | | | CCA(Granted-Unit)|
| | | CCA(Granted-Unit)|<===================|
| Restrictions ->+ |<===================| |
| removed | | |
| : | | |
| OR | CCR(Update) | |
| Validity-Time ->|------------------->| CCR(Update) |
| expires | |------------------->|
| | | CCA(Granted-Unit)|
| | CCA(Granted-Unit)|<-------------------|
| Restrictions ->|<-------------------| |
| removed | | |
Figure 5: Optional graceful service termination procedure
5.6.1 Terminate Action
The Final-Unit-Indication AVP with Final-Unit-Action TERMINATE does
not include any other information. When the subscriber has consumed
the final granted units, the service element MUST terminate the
service. This is the default handling applicable whenever the credit
control client receives an unsupported Final-Unit-Action value and
MUST be supported by all the Diameter credit control client
implementations conforming to this specification. A final Credit-
Control-Request message to the credit control server MUST be sent if
the Final-Unit-Indication AVP indicating action TERMINATE was present
at command level. The CC-Request-Type AVP in the request is set to
the value TERMINATION_REQUEST.
5.6.2 Redirect Action
The Final-Unit-Indication AVP with Final-Unit-Action REDIRECT
indicates to the service element supporting this action that, upon
consumption of the final granted units, the user MUST be re-directed
to the address specified in the Redirect-Server AVP as follows.
The credit control server sends the Redirect-Server AVP in the
Credit-Control-Answer message. In such a case the service element
MUST redirect or connect the user to the destination specified in the
Redirect-Server AVP, if possible. When the end user is redirected (by
using other protocols than Diameter) to the specified server or
connected to the top-up server, an additional authorization (and
possibly authentication) may be needed before the subscriber can
replenish the account, however, this is out of the scope of this
specification.
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In addition to the Redirect-Server AVP, the credit control server MAY
include one or more Restriction-Filter-Rule AVP or one or more
Filter-Id AVP in the Credit-Control-Answer message in order to enable
the user to access other services (for example zero-rated services).
In such a case the access device MUST drop all the packets not
matching the IP filters specified in the Credit-Control-Answer
message and redirect the user to the destination specified in the
Redirect-Server AVP, if possible.
Another entity than the credit control server may provision the
access device with appropriate IP packet filters to be used in
conjunction with the Diameter credit control application. This case
is considered in section 5.6.3.
When the final granted units have been consumed the credit control
client MUST perform an intermediate interrogation. The purpose of
this intermediate interrogation is to indicate to the credit control
server that the specified action started and to report the used
units. The credit control server MUST deduct the used amount from the
end user's account but MUST NOT make a new credit reservation. The
credit control client, however, may send intermediate interrogations
before all the final granted units have been consumed for which
rating and money reservation may be needed, for instance upon
Validity-Time expires or upon mid-session service event that affect
the rating of the current service. Therefore, the credit control
client MUST NOT include any rating related AVP in the request sent
upon all the final granted units have been consumed as a hint to the
server that the requested final unit action started, rating and money
reservation are not required (when the Multiple-Services-Credit-
Control AVP is used, the Service-Identifier or Rating-Group AVPs is
included to indicate the concerned services). Naturally, the Credit-
Control-Answer message does not contain any granted service unit and
MUST include the Validity-Time AVP to indicate to the credit control
client how long the subscriber is allowed to use network resources
before a new intermediate interrogation is sent to the server.
At the expiry of Validity-Time the credit control client sends a
Credit-Control-Request (UPDATE_REQUEST) as usual. This message does
not include the Used-Service-Unit AVP since there is no allotted
quota to report. The credit control server processes the request and
MUST perform the credit reservation. If during this time the
subscriber did not replenish his/her account whether he/she will be
disconnected or will be granted access to services not controlled by
credit control server for unlimited time is dependent on the home
service provider policy (note: the latter option implies that the
service element should not remove the restriction filters upon
termination of the credit control). The server will return the
appropriate Result-Code (see section 9.1) in the Credit-Control-
Answer message in order to implement the policy-defined action.
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Otherwise new quota will be returned, the service element MUST remove
all the possible restrictions activated by the graceful service
termination process and continue the credit control session and the
service session as usual.
The credit control client may not wait until the expiration of the
Validity-Time and may send a spontaneous updating (a new Credit-
Control-Request) if the service element can determine for instance
that communication between the end user and the top-up server took
place. An example of this is given in Appendix A (Figure A.8).
It is worth noting that the credit control server may initiate the
above-described process already for the first interrogation. However,
the user's account might be empty at the time when the first
interrogation is performed. In this case the subscriber can be
offered a chance to replenish the account and continue the service.
The credit control client receives a Credit-Control-Answer or service
specific authorization answer with the Final-Unit-Indication AVP,
Validity-Time AVP but no Granted-Unit. In such a case it immediately
starts the graceful service termination without sending any message
to the server. An example of this case is illustrated in Appendix A.
5.6.3 Restrict Access Action
The Final-Unit-Indication AVP with Final-Unit-Action RESTRICT_ACCESS
indicates to the access device supporting this action that the user
MUST be restricted access according to the IP packet filters given in
the Restriction-Filter-Rule AVP(s) or according to the IP packet
filters identified by the Filter-Id AVP(s). The credit control server
SHOULD include either the Restriction-Filter-Rule AVP or the Filter-
Id AVP in the Credit-Control-Answer message.
Another entity than the credit control server may provision the
access device with appropriate IP packet filters to be used in
conjunction with the Diameter credit control application. Such an
entity, for instance, may configure the access device with IP flows
that are to be passed when the Diameter credit control application
indicates RESTRICT_ACCESS or REDIRECT. The access device passes IP
packets according to the filter rules possibly received in the
Credit-Control-Answer message in addition to the filter rules
possibly configured by the other entity. However, the action to be
taken when the user's account cannot cover the cost of the requested
service is the responsibility of the credit control server that
controls the prepaid subscriber.
If another entity working in conjunction with the Diameter Credit
Control application already provisions the access device with all the
required filter rules for the end user, it is presumably not needed
for the credit control server to send any additional filter.
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Therefore it is RECOMMENDED that credit control server
implementations supporting the graceful service termination can be
configurable whether to send the Restriction-Filter-Rule AVP, the
Filter-Id AVP or none of the above.
When the final granted units have been consumed, the credit control
client MUST perform an intermediate interrogation. The credit control
client and the credit control server process this intermediate
interrogation and execute subsequent procedures as specified in the
previous section for the REDIRECT action.
The credit control server may initiate the graceful service
termination with action RESTRICT_ACCESS already for the first
interrogation as specified in the previous section for the REDIRECT
action.
5.6.4 Usage of the Server-Initiated Credit Re-Authorization
Once the subscriber replenishes the account she presumably expects
all the restrictions placed by the graceful termination procedure be
immediately removed and unlimited services' access be resumed. For
the best user experience the credit control server implementation MAY
support the server-initiated credit re-authorization (see section
5.5). In such a case, upon the successful account top-up took place,
the credit control server sends the Re-Auth-Request (RAR) message to
solicit the credit re-authorization. The credit control client
initiates the credit re-authorization by sending the Credit- Control-
Request message with the CC-Request-Type AVP set to the value
UPDATE_REQUEST. The Used-Service-Unit AVP is not included in the
request since there is no allotted quota to report. The Requested-
Service-Unit AVP MAY be included in the request. After the credit
control client successfully receives the Credit-Control-Answer with
new Granted-Service-Unit all the possible restrictions activated for
the purpose of the graceful service termination MUST be removed in
the service element, the credit control session and the service
session continue as usual.
5.7 Failure Procedures
The Credit-Control-Failure-Handling AVP (CCFH) as described in this
section determines the behavior of the credit control client in fault
situations. The CCFH may be received from the Diameter home AAA
server, from the credit control server or may be locally configured.
The CCFH value received from the home AAA server overrides the
locally configured value and the CCFH value received from the credit
control server in the Credit-Control-Answer message always override
any already existing value.
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The authorization server MAY include the Accounting-Realtime-Required
AVP to determine what to do if the sending of accounting records to
the accounting server has been temporarily prevented as defined in
[DIAMBASE]. It is RECOMMENDED that the client complement the credit-
control failure procedures with backup accounting flow towards an
accounting server. Using different combinations of Accounting-
Realtime-Required and Credit-Control-Failure-Handling AVPs different
safety levels can be built. For example by choosing the Credit-
Control-Failure-Handling AVP equal to CONTINUE for the credit control
flow and Accounting-Realtime-Required AVP equal to DELIVER_AND_GRANT
for the accounting flow, the service can be granted to the end user
even if the connection to the credit-control server is down but the
accounting server is able to collect the accounting information,
provided that there is information exchange taking place between the
accounting server and credit-control server.
Since the credit-control application is based on real-time bi-
directional communication between the credit-control client and the
credit-control server, the usage of alternative destinations and the
buffering of messages may not be sufficient in the event of
communication failures. Since the credit-control server has to
maintain session states, moving the credit-control message stream to
a backup server requires a complex context transfer solution. Whether
the credit-control message stream is moved to a backup credit-control
server during an ongoing credit-control session depends on the value
of the CC-session-Failover AVP. However, failover may occur at any
point in the path between credit-control client and credit-control
server in the event that a transport failure is detected with a peer,
as described in [DIAMBASE]. As a consequence the credit-control
server might receive duplicate messages. These duplicates or out of
sequence messages can be detected in the credit-control server based
on the credit-control server session state machine (section 7),
Session-Id AVP and CC-Request-Number AVP.
If a failure occurs during an ongoing credit-control session, the
credit-control client may move the credit control message stream to
an alternative server if the CC-server indicated FAILOVER_SUPPORTED
in the CC-Session-Failover AVP. A secondary credit control server
name, received from the home Diameter AAA server or locally
configured, can be used as an address of the backup server. If the
CC-Session-Failover AVP is set to FAILOVER_NOT SUPPORTED the credit
control message stream MUST NOT be moved to backup server.
For new credit control sessions, failover to an alternative credit-
control server SHOULD be performed if possible. For instance, if an
implementation of the credit control client can determine primary
credit control server unavailability it can establish the new credit
control sessions with a possibly available secondary credit control
server.
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The AAA transport profile [AAATRANS] defines the application layer
watchdog algorithm that enables failover from a peer that has failed
and is controlled by a watchdog timer (Tw) defined in [AAATRANS]. The
recommended default initial value for Tw (Twinit) is 30 seconds.
Twinit may be set as low as 6 seconds, however, according to
[AAATRANS] setting too low value for Twinit is likely to result in an
increased probability of duplicates, as well as an increase in
spurious failover and failback attempts. Since the Diameter base
protocol is common to several different types of Diameter AAA
applications that may be run in the same service element, tuning the
timer Twinit to a lower value in order to satisfy the requirements of
real-time applications, such as the Diameter Credit Control
application, will certainly materialize the above mentioned problems.
For prepaid services, however, the end user expects an answer from
the network in a reasonable time, thus the Diameter credit control
client shall react faster than the underlying base protocol.
Therefore this specification defines the timer Tx that is used by the
credit-control client (as defined in section 13) to supervise the
communication with the credit-control server. When the timer Tx
elapses the credit-control client takes an action to the end user
according to the Credit-Control-Failure-Handling AVP.
When Tx expires, the Diameter credit control client always terminates
the service if the Credit-Control-Failure-Handling (CCFH) AVP is set
to the value TERMINATE. The credit control session may be moved to an
alternative server only in case a protocol error DIAMETER_TOO_BUSY or
DIAMETER_UNABLE_TO_DELIVER is received before Tx expires, therefore,
the value TERMINATE is not appropriate if proper failover behavior is
desired.
If the Credit-Control-Failure-Handling AVP is set to the value
CONTINUE or RETRY_AND_TERMINATE, the service will be granted to the
end user upon the timer Tx expires. An answer message with granted-
units may arrive later on due to the base protocol transport failover
occurred in the path to the Credit Control Server (Twinit default
value is 3 times more than the Tx recommended value). The credit
control client SHOULD grant the service to the end user, start
monitoring the resource usage and wait for the possible late answer
until the timeout of the request (e.g. 120 seconds). If the request
fails and the CC-Session-Failover AVP is set to FAILOVER_NOT
SUPPORTED, the credit control client terminates or continues the
service depending on the value set in the CCFH and MUST free all the
reserved resources for the credit control session. If a protocol
error DIAMETER_UNABLE_TO_DELIVER or DIAMETER_TOO_BUSY is received or
the request timeout and the CC-Session-Failover AVP is set to
FAILOVER SUPPORTED, the credit control client MAY send the request to
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a backup server if possible. If the credit control client receives a
successful answer from the backup server, it continues the credit
control session with such a server. If also the re-transmitted
request fails, the credit control client terminates or continues the
service depending on the value set in the CCFH and MUST free all the
reserved resources for the credit control session.
If a communication failure occurs during the graceful service
termination procedure, the service element SHOULD always terminate
the ongoing service session.
If the credit-control server detects a failure during an ongoing
credit-control session, it will terminate the credit-control session
and return the reserved units back to the end user's account.
The supervision session timer Tcc (as defined in section 13) is used
in the credit-control server to supervise the credit-control session.
In order to support the failover between credit control servers
information transfer about the credit control session and account
state SHOULD take place between the primary and the secondary credit
control server. Implementations supporting the credit control session
failover MUST also ensure proper detection of duplicate or out of
sequence messages. The communication between the servers is regarded
as an implementation issue and is outside of the scope of this
specification.
6. One Time Event
The one-time event is used when there is no need to maintain any
state in the Diameter credit-control server, for example enquiring
the price of the service. The use of one-time event implies that the
user has been authenticated and authorized beforehand.
The one time event can be used when the credit-control client wants
to know the cost of the service event without any credit-reservation
or to check the account balance without any credit-reservation. It
can be used also for refunding service units on the user's account or
direct debiting without any credit-reservation. The one time event is
shown in Figure 6.
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Diameter
End-User Service Element AAA Server CC Server
(CC Client)
| Service Request | | |
|------------------>| | |
| | CCR(Event) | |
| |------------------->| CCR(Event) |
| | |------------------->|
| | | CCA(Granted-Units)|
| | CCA(Granted-Units)|<-------------------|
| Service Delivery |<-------------------| |
|<----------------->| | |
Figure 6: One time event
In environments such as the 3GPP architecture the one time event can
be sent from the service element directly to the credit-control
server.
6.1 Service Price Enquiry
The credit-control client may need to know the price of the service
event. There might exist services offered by application service
providers, whose prices are not known in the credit-control client.
End user might also want to get an estimation of the price of a
service event before requesting it.
A Diameter credit-control client requesting the cost information MUST
set the CC-Request-Type AVP equal to EVENT_REQUEST, include the
Requested-Action AVP set to PRICE_ENQUIRY and set the requested
service event information into the Service-Identifier AVP in the
Credit-Control-Request message. Additional service event information
may be sent as service specific AVPs or may be sent within the
Service-Parameter-Info AVP.
The credit-control server calculates the cost of the requested
service event, but it does not perform any account balance check or
credit-reservation from the account.
The estimated cost of the requested service event is returned to the
credit-control client in the Cost-Information AVP in the Credit-
Control-Answer message.
6.2 Balance Check
The Diameter credit-control client may need only to verify that the
end user's account balance covers the cost for a certain service
without reserving any units from the account at the time of the
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inquiry. This method does not guarantee that there would be credit
left when the Diameter credit-control client requests the debiting of
the account with a separate request.
A Diameter credit-control client requesting the balance check MUST
set the CC-Request-Type AVP equal to EVENT_REQUEST, include
Requested-Action AVP set to CHECK_BALANCE and include the
Subscription-Id AVP to identify the End-User in the credit-control
server.
The credit-control server makes the balance check, but it does not do
any credit-reservation from the account.
The result of balance check (ENOUGH_CREDIT/NO_CREDIT) is returned to
the credit-control client in the Check-Balance-Result AVP in the
Credit-Control-Answer message.
6.3 Direct Debiting
There are certain service events for which service execution is
always successful in the service environment. The delay between the
service invocation and the actual service delivery to the end user
can be sufficiently long that the use of the session-based credit-
control would lead to unreasonable long credit-control sessions. In
these cases the Diameter credit-control client can use the one-time
event scenario for direct debiting. The Diameter credit-control
client SHOULD be sure that the requested service event execution
would be successful, when this scenario is used.
The CC-Request-Type is set to the value EVENT_REQUEST and the
Requested-Action AVP set to DIRECT_DEBITING in the Credit-Control-
Request message. The Subscription-Id AVP SHOULD be included to
identify the End-User in the credit-control server. The Event-
Timestamp AVP contains the time when the service event is requested
in the service element.
The Diameter credit-control client MAY include the monetary amount to
be charged in the Requested-Service-Unit AVP, if it knows the cost of
the service event. If the Diameter credit-control client does not
know the cost of the service event, the Requested-Service-Unit AVP
MAY contain the number of requested service events. The Service-
Identifier AVP always indicates the concerned service, additional
service event information to be rated MAY be sent as service specific
AVPs or MAY be sent within the Service-Parameter-Info AVP.
The credit-control server SHOULD rate the service event and deduct
the corresponding monetary amount from end user's account. If the
type of the Requested-Service-Unit AVP is money, no rating is needed
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but the corresponding monetary amount is deducted from the End User's
account.
The credit-control server returns the Granted-Service-Unit AVP in the
Answer message to the Diameter credit-control client. The Granted-
Service-Unit AVP contains the amount of service units that the
Diameter credit-control client can provide to the end user. The type
of the Granted-Service-Unit can be time, volume, service specific or
money depending on the type of service event.
If the credit-control server determines that no credit-control is
needed for the service it can include the result code indicating that
the credit-control is not applicable (e.g. service is free of
charge).
For informative purposes, the Credit-Control-Answer message MAY also
include the Cost-Information AVP containing the estimated total cost
of the requested service.
6.4 Refund
Some services may refund service units to the end user's account, for
example gaming services.
The credit-control client MUST set CC-Request-Type to the value
EVENT_REQUEST and the Requested-Action AVP to REFUND in the Credit-
Control-Request message. The Subscription-Id AVP SHOULD be included
to identify the End-User in the credit-control server.
The Diameter credit-control client MAY include the monetary amount to
be refunded in the Requested-Service-Unit AVP. The Service-Identifier
AVP always indicates the concerned service. If the Diameter credit-
control client does not know the monetary amount to be refunded, in
addition to the Service-Identifier AVP it MAY send service specific
AVPs or the Service-Parameter-Info AVP containing additional service
event information to be rated.
For informative purposes, the Credit-Control-Answer message MAY also
include the Cost-Information AVP containing the estimated monetary
amount of refunded unit.
6.5 Failure Procedure
Failover to an alternative credit-control server is allowed for one
time event since the server is not maintaining session states, for
instance, if the credit control client receives a protocol error
DIAMETER_UNABLE_TO_DELIVER or DIAMETER_TOO_BUSY it can re-send the
request to an alternative server if possible. There MAY exist
protocol transparent Diameter relays and redirect agents or Diameter
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credit-control proxies between credit-control client and credit-
control server. Failover may occur at any point in the path between
credit-control client and credit-control server in the event that a
transport failure is detected with a peer, as described in
[DIAMBASE]. Because there can be duplicate requests for various
reasons the credit-control server is therefore responsible for the
real time duplicate detection. Implementation issues for duplicate
detection are discussed in [DIAMBASE] Appendix C.
When the credit-control client detects a communication failure to the
credit-control server, its behavior depends on the requested action.
The timer Tx (as defined in section 13) is used in the credit-control
client to supervise the communication with the credit-control server.
In case the requested action is PRICE_ENQUIRY or BALANCE_CHECK and
communication failure is detected the credit-control client SHOULD
forward the request messages to an alternative credit-control server,
if possible. The secondary Credit control server name, if received
from the home Diameter AAA server, can be used as an address of
backup server.
If the requested action is DIRECT_DEBITING the Direct-Debiting-
Failure-Handling AVP (DDFH) controls the credit control client
behavior. The DDFH may be received from the home Diameter AAA server
or may be locally configured. The credit control server may also send
the DDFH in any CCA message to be used for direct debiting events
compiled thereafter. The DDFH value received from the home Diameter
AAA server overrides the locally configured value and the DDFH value
received from the credit control server in a Credit-Control-Answer
message always override any already existing value. If the DDFH is
set to TERMINATE_OR_BUFFER, the credit-control client SHOULD NOT
grant the service if it can determine, eventually after a possible
re-transmission attempt to an alternative credit control server, from
the result code or error code in the answer message that units have
not been debited. Otherwise the credit-control client SHOULD grant
the service to the end user and store the request in the credit-
control application level non-volatile storage (Note that re-sending
the request at a later time is not a guarantee that the service will
be debited, since the user's account may be empty at the time when
the server successfully processes the request). The credit-control
client MUST mark these request messages as possible duplicate by
setting the T-flag in the command header as described in [DIAMBASE]
section 3. If the Direct-Debiting-Failure-Handling AVP is set to
CONTINUE, the service SHOULD be granted even if credit-control
messages cannot be delivered and messages are not buffered.
If the timer Tx expires the credit-control client MUST continue the
service and wait for a possible late answer. If the request timeout
the credit control client re-transmit the request (marked with T-
flag) to a backup credit control server if possible. In the event
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that also the re-transmitted request timeout or a temporary error is
received in answer to such a request, the credit control client
buffers the request if the value of the Direct-Debiting-Failure-
Handling AVP is set to TERMINATE_OR_BUFFER. If a failed answer is
received for the re-transmitted request, the credit control client
frees all the resources reserved for the event message and deletes
the request regardless the value of the DDFH.
The Credit-Control-Request with requested action REFUND should always
be stored in the credit-control application level non-volatile
storage in case of temporary failure. The credit-control client MUST
mark the re-transmitted request message as possible duplicate by
setting the T-flag in the command header as described in [DIAMBASE]
section 3.
For stored requests, the implementation may choose to limit the
number of re-transmission attempts and define a re-transmission
interval.
It should be noted that only one place in the credit-control system
SHOULD be responsible for duplicate detection. If there is only one
credit-control server within the given realm, the credit-control
server may perform duplicate detection. In case when more than one
credit-control servers are serving a given realm, only one entity in
the credit control system should be responsible to ensure that the
end user's account is not debited or credited multiple times for the
same service event.
7. Credit Control Application State Machine
This section defines the credit control application state machine.
The first four state machines are to be observed by credit-control
clients. The first one describes the session-based credit-control
when the first interrogation is executed as part of the
authorization/authentication process. The second one describes the
session-based credit-control when the first interrogation is executed
after the authorization/authentication process. The requirements what
state machine need to be supported are discussed in section 5.2.
The third state machine describes the session-based credit-control
for intermediate and final interrogations. The fourth one describes
the event-based credit-control. These latter state machines are to be
observed by all the implementations that conform to this
specification.
The fifth state machine describes the credit-control session from a
credit-control server perspective.
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Any event not listed in the state machines MUST be considered as an
error condition, and a corresponding answer, if applicable, MUST be
returned to the originator of the message.
In the state table, the event 'Failure to send' means that the
Diameter credit-control client is unable to communicate with the
desired destination or with a possibly defined alternative
destination in case failover procedure is supported (e.g. the request
timeout and the answer message is not received). This could be due to
the peer being down, or due to a physical link failure in the path
to/from the credit-control server.
The event 'Temporary error' means that the Diameter credit-control
client received a protocol error notification DIAMETER_TOO_BUSY,
DIAMETER_UNABLE_TO_DELIVER or DIAMETER_LOOP_DETECTED in the Result-
Code AVP of the Credit-Control-Answer command. The above protocol
error notification may be ultimately received in answer to the re-
transmitted request to a possibly defined alternative destination if
failover is supported.
The event 'Failed answer' means that the Diameter credit-control
client received non-transient failure (permanent failure)
notification in the Credit-Control-Answer command. The above
permanent failure notification may be ultimately received in answer
to the re-transmitted request to a possibly defined alternative
destination if failover is supported.
The action 'store request' means that a request is stored in the
credit-control application level non-volatile storage.
The event 'Not successfully processed' means that the credit-control
server could not process the message, e.g. due to unknown end user,
account being empty or due to errors defined in [DIAMBASE].
The Tx timer, which is used to control the waiting time in the Credit
control client in the PENDING state, is stopped when exiting the
Pending state. The stopping of the Tx timer is omitted in the state
machine when the new state is Idle since moving to Idle state implies
the clearing of the session and all the variables associated to it.
The states PendingI, PendingU, PendingT PendingE and PendingB stand
for pending states to wait for an answer to a credit control request
related to Initial, Update, Termination, Event or Buffered request
respectively.
The abbreviations CCFH and DDFH stand for Credit-Control-Failure-
Handling and Direct-Debiting-Failure-Handling respectively.
In the following state machine table the failover to a possibly
secondary server upon 'Temporary error' or 'Failure to send' is not
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explicitly described. Moving an ongoing credit control message stream
to an alternative server is, however, possible if the CC-Session-
Failover AVP is set to FAILOVER_SUPPORTED as described in section
5.7.
Re-sending a credit control event to an alternative server is
supported as described in section 6.5.
CLIENT, SESSION BASED for the first interrogation with AA request
State Event Action New State
---------------------------------------------------------------
Idle Client or device requests Send PendingI
access/service AA request
with added
CC AVPs,
start Tx
PendingI Successful AA req. Grant Open
answer received service to
end user,
stop Tx
PendingI Tx expired Disconnect Idle
user/dev
PendingI Failed AA answer received Disconnect Idle
user/dev
PendingI AA answer Grant Idle
received with result code service
equal to credit-control N/A to end user
PendingI User service terminated Queue PendingI
termination
event
PendingI Change in rating condition Queue PendingI
changed
rating
condition
event
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CLIENT, SESSION BASED for the first interrogation with CCR
State Event Action New State
----------------------------------------------------------------
Idle Client or device requests Send PendingI
access/service CC initial
req.,
start Tx.
PendingI Successful CC initial Stop Tx Open
answer received
PendingI Failure to send, or Grant Idle
temporary error and service to
CCFH equal to CONTINUE end user
PendingI Failure to send, or Terminate Idle
temporary error and end user's
CCFH equal to TERMINATE service
or equal to RETRY_AND_TERMINATE
PendingI Tx expired and CCFH Terminate Idle
equal to TERMINATE end user's
service
PendingI Tx expired and CCFH equal Grant PendingI
to CONTINUE or equal to service to
RETRY_AND_TERMINATE end user
PendingI CC initial answer Terminate Idle
received with result code end user's
SERVICE_ DENIED or service
USER_UNKNOWN
PendingI CC initial answer Grant Idle
received with result code service
equal to credit-control N/A to end user
PendingI Failed CC initial answer Grant Idle
received CCFH equal to Service to
CONTINUE end user
PendingI Failed CC initial answer Terminate Idle
received and CCFH equal end user's
to TERMINATE or equal to service
RETRY_AND_TERMINATE
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PendingI User service terminated Queue PendingI
termination
event
PendingI Change in rating condition Queue PendingI
changed
rating
condition
event
CLIENT, SESSION BASED for intermediate and final interrogations
State Event Action New State
----------------------------------------------------------------
Open Granted unit elapses Send PendingU
and no final unit CC update
indication received req.,
start Tx.
Open Granted unit elapses Terminate PendingT
and final unit action end user's
equal to TERMINATE service, send
received CC termination
req.
Open Change in rating condition Send PendingU
in queue CC update
req.,
Start Tx.
Open Service terminated in queue Send PendingT
CC termination
req.
Open Change in rating condition Send PendingU
or Validity-Time elapses CC update
req.,
Start Tx.
Open User service terminated Send PendingT
CC termination
req.
Open RAR received Send RAA PendingU
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followed by
CC update req.,
start Tx
PendingU Successful CC update Stop Tx Open
answer received
PendingU Failure to send, or Grant Idle
temporary error and service to
CCFH equal to CONTINUE end user
PendingU Failure to send, or Terminate Idle
temporary error and end user's
CCFH equal to TERMINATE service
or equal to RETRY_AND_TERMINATE
PendingU Tx expired and CCFH Terminate Idle
equal to TERMINATE end user's
service
PendingU Tx expired and CCFH equal Grant PendingU
to CONTINUE or equal to service to
RETRY_AND_TERMINATE end user.
PendingU CC update answer Terminate Idle
received with result code end user's
SERVICE_DENIED service
PendingU CC update answer Grant Idle
received with result code service
equal to credit-control N/A to end user
PendingU Failed CC update Grant Idle
answer received and service to
CCFH equal to CONTINUE end user.
PendingU Failed CC update Terminate Idle
answer received CCFH end user's
equal to TERMINATE or service
equal to RETRY_AND_TERMINATE
PendingU User service terminated Queue PendingU
termination
event
PendingU Change in rating Queue PendingU
condition changed
rating
condition
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event
PendingU RAR received Send RAA PendingU
PendingT Successful CC Idle
termination answer received
PendingT Failure to send, or temporary Idle
error or failed answer
PendingT Change in rating condition PendingT
CLIENT, EVENT BASED
State Event Action New State
----------------------------------------------------------------
Idle Client or device requests Send PendingE
a one-time service CC event
req.,
Start Tx.
Idle Request in storage Send PendingB
stored
request
PendingE Successful CC event Grant Idle
answer received service to
end user
PendingE Failure to send, temporary Indicate Idle
error or failed CC event service
answer received, or error
Tx expired, requested
action BALANCE_CHECK or
PRICE_ENQUIRY
PendingE CC event answer Terminate Idle
received with result code end user's
SERVICE_DENIED or service
USER_UNKNOWN and Tx running
PendingE CC event answer Grant Idle
received with result code service
credit-control N/A, requested to end
action DIRECT_DEBITING user
PendingE Failure to send, temporary Grant Idle
error or failed CC event service
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answer received, requested to end
action DIRECT_DEBITING and user
DDFH equal to CONTINUE
PendingE Failed CC event Terminate Idle
answer received or temporary end user's
error, requested action service
DIRECT_DEBITING and
DDFH equal to
TERMINATE_OR_BUFFER and
Tx running
PendingE Tx expired, requested Grant PendingE
action DIRECT_DEBITING service
to end
user
PendingE Failure to send, requested Store Idle
action DIRECT_DEBITING and request with
DDFH equal to T-flag
TERMINATE_OR_BUFFER
PendingE Temporary error, requested Store Idle
action DIRECT_DEBITING and request
DDFH equal to
TERMINATE_OR_BUFFER and
Tx expired
PendingE Failed answer or answer Idle
received with result code
SERVICE DENIED or USER_UNKNOWN,
requested action
DIRECT_DEBITING and Tx expired
PendingE Failed CC event answer Indicate Idle
received, requested service
action REFUND_ACCOUNT error and
delete request
PendingE Failure to send or Store Idle
Tx expired, requested request
action REFUND_ACCOUNT with T-flag
PendingE Temporary error Store Idle
and requested action request
REFUND_ACCOUNT
PendingB Successful CC answer Delete Idle
received request
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PendingB Failed CC answer Delete Idle
received request
PendingB Failure to send or Idle
temporary error
SERVER, SESSION AND EVENT BASED
State Event Action New State
----------------------------------------------------------------
Idle CC initial request Send Open
received and successfully CC initial
processed. answer,
reserve units,
start Tcc
Idle CC initial request Send Idle
received, but not CC initial
successfully processed. answer with
Result-Code
!= SUCCESS
Idle CC event request Send Idle
received and successfully CC event
processed. answer
Idle CC event request Send Idle
received, but not CC event
successfully processed. answer with
Result-Code
!= SUCCESS
Open CC update request Send CC Open
received and successfully update answer,
processed debit used
units and
reserve
new units,
Restart Tcc
Open CC update request Send Idle
received, but not CC update
successfully processed. answer with
Result-Code
!= SUCCESS,
debit used
units
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Open CC termination request Send Idle
received, and successfully CC termin.
processed answer,
Stop Tcc,
debit used
units
Open CC termination request Send Idle
received, but not CC termin.
successfully processed. answer with
Result-Code
!= SUCCESS,
debit used
units
Open Session supervision timer Tcc release Idle
expired reserved
units
8. Credit Control AVPs
This section defines the credit-control AVPs that are specific to
Diameter Credit-control Application and MAY be included in the
Diameter credit control messages.
The AVPs defined in this section MAY also be included in
authorization commands defined in authorization specific
applications, such as [NASREQ] and [DIAMMIP], in case the first
interrogation is performed as part of the authorization /
authentication process as described in section 5.2.
The Diameter AVP rules are defined in the Diameter Base [DIAMBASE],
section 4. These AVP rules are observed in AVPs defined in this
section.
The following table describes the Diameter AVPs defined in Credit-
control application, their AVP Code values, types, possible flag
values and whether the AVP MAY be encrypted. The Diameter base
[DIAMBASE] specifies in the section 4.5 the AVP Flag rules for AVPs.
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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST| |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
CC-Correlation-Id TBD 8.1 OctetString| | P,M | | V | Y |
CC-Input-Octets TBD 8.24 Unsigned64 | M | P | | V | Y |
CC-Money TBD 8.22 Grouped | M | P | | V | Y |
CC-Output-Octets TBD 8.25 Unsigned64 | M | P | | V | Y |
CC-Request-Number TBD 8.2 Unsigned32 | M | P | | V | Y |
CC-Request-Type TBD 8.3 Enumerated | M | P | | V | Y |
CC-Service- TBD 8.26 Unsigned64 | M | P | | V | Y |
Specific-Units | | | | | |
CC-Session- TBD 8.4 Enumerated | M | P | | V | Y |
Failover | | | | | |
CC-Sub-Session-Id TBD 8.5 Unsigned64 | M | P | | V | Y |
CC-Time TBD 8.21 Unsigned32 | M | P | | V | Y |
CC-Total-Octets TBD 8.23 Unsigned64 | M | P | | V | Y |
CC-Unit-Type TBD 8.32 Enumerated | M | P | | V | Y |
Check-Balance- TBD 8.6 Enumerated | M | P | | V | Y |
Result | | | | | |
Cost-Information TBD 8.7 Grouped | M | P | | V | Y |
Cost-Unit TBD 8.12 UTF8String | M | P | | V | Y |
Credit-Control TBD 8.13 Enumerated | M | P | | V | Y |
Credit-Control- TBD 8.14 Enumerated | M | P | | V | Y |
Failure-Handling | | | | | |
Currency-Code TBD 8.18 Unsigned32 | M | P | | V | Y |
Direct-Debiting TBD 8.19 Enumerated | M | P | | V | Y |
Failure-Handling | | | | | |
Exponent TBD 8.9 Integer32 | M | P | | V | Y |
Final-Unit-Action TBD 8.35 Enumerated | M | P | | V | Y |
Final-Unit- TBD 8.34 Grouped | M | P | | V | Y |
Indication | | | | | |
Granted-Service- TBD 8.17 Grouped | M | P | | V | Y |
Unit | | | | | |
G-S-U-Pool- TBD 8.32 Unsigned32 | M | P | | V | Y |
Identifier | | | | | |
G-S-U-Pool- TBD 8.25 Grouped | M | P | | V | Y |
Reference | | | | | |
Multiple-Services TBD 8.16 Grouped | M | P | | V | Y |
-Credit-Control | | | | | |
Multiple-Services TBD 8.40 Enumerated | M | P | | V | Y |
-Indicator | | | | | |
Rating-Group TBD 8.29 Unsigned32 | M | P | | V | Y |
Redirect-Address TBD 8.38 Enumerated | M | P | | V | Y |
-Type | | | | | |
Redirect-Server TBD 8.37 Grouped | M | P | | V | Y |
Redirect-Server TBD 8.39 UTF8String | M | P | | V | Y |
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-Address | | | | | |
Requested-Action TBD 8.41 Enumerated | M | P | | V | Y |
Requested-Service TBD 8.18 Grouped | M | P | | V | Y |
Unit | | | | | |
Restriction TBD 8.36 IPFiltrRule| M | P | | V | Y |
-Filter-Rule | | | | | |
Service- TBD 8.28 UTF8String | M | P | | V | Y |
Identifier | | | | | |
Service-Parameter TBD 8.42 Grouped | | P,M | | V | Y |
-Info | | | | | |
Service- TBD 8.43 Unsigned32 | | P,M | | V | Y |
Parameter-Type | | | | | |
Service- TBD 8.44 OctetString| | P,M | | V | Y |
Parameter-Value | | | | | |
Subscription-Id TBD 8.45 Grouped | M | P | | V | Y |
Subscription-Id TBD 8.47 UTF8String | M | P | | V | Y |
-Data | | | | | |
Subscription-Id TBD 8.46 Enumerated | M | P | | V | Y |
-Type | | | | | |
Tariff-Change TBD 8.27 Enumerated | M | P | | V | Y |
-Usage | | | | | |
Tariff-Time TBD 8.20 Time | M | P | | V | Y |
-Change | | | | | |
Unit-Value TBD 8.8 Grouped | M | P | | V | Y |
Used-Service-Unit TBD 8.19 Grouped | M | P | | V | Y |
User-Equipment TBD 8.48 Grouped | | P,M | | V | Y |
-Info | | | | | |
User-Equipment TBD 8.49 Enumerated | | P,M | | V | Y |
-Info-Type | | | | | |
User-Equipment TBD 8.50 OctetString| | P,M | | V | Y |
-Info-Value | | | | | |
Value-Digits TBD 8.10 Integer64 | M | P | | V | Y |
Validity-Time TBD 8.33 Unsigned32 | M | P | | V | Y |
[IANA please fill in the TBA values in this table with appropriate
AVP codes, suggested values listed below and remove this note.]
8.1 CC-Correlation-Id AVP
The CC-Correlation-Id AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 411) is of type OctetString and
contains information to correlate credit control requests generated
for different components of the service, e.g. transport and service
level. The one who allocates the Service-Identifier, i.e. unique
identifier of a service, is also responsible to define the content
and encoding of the CC-Correlation-Id AVP.
8.2 CC-Request-Number AVP
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The CC-Request-Number AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 415) is of type Unsigned32 and
identifies this request within one session. As Session-Id AVPs are
globally unique, the combination of Session-Id and CC-Request-Number
AVPs is also globally unique, and can be used in matching credit
control messages with confirmations. An easy way to produce unique
numbers is to set the value to 0 for credit control request of type
INITIAL_REQUEST and EVENT_REQUEST, and set the value to 1 for the
first UPDATE_REQUEST, 2 for the second, and so on until the value for
TERMINATION_REQUEST.
8.3 CC-Request-Type AVP
The CC-Request-Type AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 416) is of type Enumerated and
contains the reason for sending the Credit-control request message.
It MUST be present in all CC-Request messages. The following values
are defined for the CC-Request-Type AVP:
INITIAL_REQUEST 1
A Credit-control Initial request is used to initiate a credit
control session, and contains credit control information that is
relevant to the initiation of the session.
UPDATE_REQUEST 2
An Update Credit-control request contains credit control
information for an existing credit control session. Update
Credit-control requests SHOULD be sent every time a credit-
control re-authorization is needed at the expiry of the allocated
quota or validity time. Further, additional service-specific
events MAY trigger a spontaneous Update request.
TERMINATION_REQUEST 3
A Credit-control Termination Request is sent to terminate a
credit-control session and contains credit control information
relevant to the existing session.
EVENT_REQUEST 4
A Credit Control Event Request is used when there is no need
to maintain any credit control session state in the credit-
control server. This request contains all information relevant to
the service, and is the only request of the service. The reason
forthe Event request is further detailed in the Requested-Action
AVP. The Requested-Action AVP MUST be included in the Credit-
Control-Request message when CC-Request-Type is set to
EVENT_REQUEST.
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8.4 CC-Session-Failover AVP
The CC-Session-Failover AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 418) is type of Enumerated and
contains information whether the moving of the credit-control message
stream to a backup server during an ongoing credit-control session is
supported. In case of communication failures, the credit control
message streams can be moved to an alternative destination if the
credit control server supports failover to an alternative server. The
secondary credit control server name, if received from the home
Diameter AAA server, can be used as an address of the backup server.
An implementation is not required to support the moving of credit
control message stream to an alternative server, since it requires
also moving of information related to the credit control session to
backup server.
The following values are defined for the CC-Session-Failover AVP:
FAILOVER_NOT_SUPPORTED 0
When the CC-Session-Failover AVP is set to FAILOVER_NOT_SUPPORTED
the Credit control message stream MUST NOT to be moved to
alternative destination in case of communication failure.
This is the default behavior if the AVP isn't included in the
reply from the authorization or credit-control server.
FAILOVER_SUPPORTED 1
When the CC-Session-Failover AVP is set to FAILOVER_SUPPORTED, the
Credit control message stream SHOULD be moved to alternative
destination in case of communication failure. The moving the
credit control message stream to backup server MAY require that
information related to the credit control session should be also
forwarded to alternative server.
8.5 CC-Sub-Session-Id AVP
The CC-Sub-Session-Id AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 419) is of type Unsigned64 and
contains the credit-control sub-session identifier. The combination
of the Session-Id and this AVP MUST be unique per sub-session, and
the value of this AVP MUST be monotonically increased by one for all
new sub-sessions. The absence of this AVP implies no sub-sessions are
in use.
8.6 Check-Balance-Result AVP
The Check Balance Result AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 422) is of type Enumerated and
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contains the result of the balance check. This AVP is applicable only
when the Requested-Action AVP indicates CHECK_BALANCE in the Credit-
Control-Request command.
The following values are defined for the Check-Balance-Result AVP.
ENOUGH_CREDIT 0
There is enough credit in the account to cover the requested
service.
NO_CREDIT 1
There isn't enough credit in the account to cover the requested
service.
8.7 Cost-Information AVP
The Cost-Information AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 423) is of type Grouped and it is
used to return the cost information of a service, which the credit
control client can transfer transparently to the end user. The
included Unit-Value AVP contains the cost estimate (always type of
money) of the service in case of price enquiry or the accumulated
cost estimation in the case of credit-control session.
The Currency-Code specifies in which currency the cost was given.
The Cost-Unit specifies the unit when the service cost is a cost per
unit (e.g. cost for the service is $1 per minute).
When the Requested-Action AVP with value PRICE_ENQUIRY is included in
the Credit-Control-Request command the Cost-Information AVP sent in
the succeeding Credit-Control-Answer command contains the cost
estimation of the requested service, without any reservation being
made.
The Cost-Information AVP included in the Credit-Control-Answer
command with the CC-Request-Type set to UPDATE_REQUEST contains the
accumulated cost estimation for the session without taking any
credit-reservation into account.
The Cost-Information AVP included in the Credit-Control-Answer
command with the CC-Request-Type set to EVENT_REQUEST or
TERMINATION_REQUEST contains the estimated total cost for the
requested service.
It has the following ABNF grammar:
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Cost-Information ::= < AVP Header: TBD >
{ Unit-Value }
{ Currency-Code }
[ Cost-Unit ]
8.8 Unit-Value AVP
Unit-Value AVP is of type Grouped (AVP Code XXX - IANA please fill in
and remove this note - suggested value 445) and specifies the units
as decimal value. The Unit-Value is a value together with an
exponent, i.e. Unit-Value = Value-Digits AVP * 10^Exponent. This
representation avoids unwanted rounding off. For example the value of
2,3 is represented as Value-Digits = 23 and Exponent = -1. The
absence of exponent part MUST be interpreted as exponent being equal
to zero.
It has the following ABNF grammar:
Unit-Value ::= < AVP Header: TBD >
{ Value-Digits }
[ Exponent ]
8.9 Exponent AVP
Exponent AVP is of type Integer32 (AVP Code XXX - IANA please fill in
and remove this note - suggested value 429) and contains the exponent
value to be applied for the Value-Digit AVP within the Unit-Value
AVP.
8.10 Value-Digits AVP
The Value-Digits AVP is of type Integer64 (AVP Code XXX - IANA please
fill in and remove this note - suggested value 447) and contains the
significant digits of the number. If decimal values are needed to
present the units, the scaling MUST be indicated with the related
Exponent AVP. For example for the monetary amount $ 0.05 the value of
Value-Digits AVP MUST be set to 5 and the scaling MUST be indicated
with the Exponent AVP set to -2.
8.11 Currency-Code AVP
The Currency-Code AVP (AVP Code XXX - IANA please fill in and remove
this note - suggested value 425) is of type Unsigned32 and contains a
currency code that specifies in which currency the values of AVPs
containing monetary units were given. It is specified using the
numeric values defined in the ISO 4217 standard [ISO4217].
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8.12 Cost-Unit AVP
The Cost-Unit AVP (AVP Code XXX - IANA please fill in and remove this
note - suggested value 424) is of type UTF8String and it is used
to display human readable string to the end user. It specifies the
applicable unit to the Cost-Information when the service cost is a
cost per unit (e.g. cost of the service is $1 per minute). The Cost-
Unit can be for instance minute, hour, day, kilobytes, megabytes etc.
8.13 Credit-Control AVP
The Credit-Control AVP (AVP Code XXX - IANA please fill in and remove
this note - suggested value 426) is of type Enumerated and MUST be
included in AA requests when service element has credit control
capabilities.
CREDIT_AUTHORIZATION 0
If the home Diameter AAA server determines the user is a prepaid
user, this value indicates that credit-control server MUST be
contacted to perform the first interrogation. The value of the
Credit-Control AVP MUST always be set to 0 in AA request sent to
perform the first interrogation and initiate a new credit-control
session.
RE_AUTHORIZATION 1
This value indicates to the Diameter AAA server that a credit-
control session is ongoing for the subscriber and the credit-
control server MUST not be contacted. The Credit-Control AVP set
to the value of 1 is to be used only when the first interrogation
has been successfully performed and the credit-control session is
ongoing (i.e. re-authorization triggered by Authorization-
Lifetime). This value MUST NOT be used in AA request sent to
perform the first interrogation.
8.14 Credit-Control-Failure-Handling AVP
The Credit-Control-Failure-Handling AVP (AVP Code XXX - IANA please
fill in and remove this note - suggested value 427) is of type
Enumerated. The credit-control client uses information in this AVP to
decide what to do if the sending of credit-control messages to the
credit-control server has been for instance temporarily prevented due
to a network problem. Depending on the service logic, the credit-
control server can order the client to terminate the service
immediately when there is a reason to believe that the service cannot
be charged, or to try failover to an alternative server, if possible,
and then either terminate or grant the service should also the
alternative connection fail.
TERMINATE 0
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When the Credit-Control-Failure-Handling AVP is set to TERMINATE
the service MUST only be granted as long as there is a connection
to the credit-control server. If the credit-control client does
not receive any Credit-Control-Answer message within the Tx timer
(as defined in section 13) the credit-control request is regarded
failed and the end user's service session is terminated.
This is the default behavior if the AVP isn't included in the
reply from the authorization or credit-control server.
CONTINUE 1
When the Credit-Control-Failure-Handling AVP is set to CONTINUE
the credit-control client SHOULD re-send the request to an
alternative server in case of transport or temporary failures,
provided that failover procedure is supported in the credit-
control server and the credit-control client, and an alternative
server is available. Otherwise, the service SHOULD be granted
even if credit-control messages can't be delivered.
RETRY_AND_TERMINATE 2
When the Credit-Control-Failure-Handling AVP is set to
RETRY_AND_TERMINATE the credit-control client SHOULD re-send the
request to an alternative server in case of transport or
temporary failures, provided that failover procedure is supported
in the credit-control server and the credit-control client, and
an alternative server is available. Otherwise, the service SHOULD
not be granted when the credit-control messages can't be
delivered.
8.15 Direct-Debiting-Failure-Handling AVP
The Direct-Debiting-Failure-Handling AVP (AVP Code XXX - IANA please
fill in and remove this note - suggested value 428) is of type
Enumerated. The credit-control client uses information in this AVP to
decide what to do if the sending of credit-control messages
(Requested-Action AVP set to Direct Debiting) to the credit-control
server has been for instance temporarily prevented due to a network
problem.
TERMINATE_OR_BUFFER 0
When the Direct-Debiting-Failure-Handling AVP is set to
TERMINATE_OR_BUFFER the service MUST be granted as long as there
is a connection to the credit-control server. If the credit-
control client does not receive any Credit-Control-Answer message
within the Tx timer (as defined in section 13) the credit-control
request is regarded failed. The client SHOULD terminate the
service if it can determine from the failed answer that units
have not been debited. Otherwise the credit-control client SHOULD
grant the service, store the request to application level non-
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volatile storage and try to re-send the request. These requests
MUST be marked as possible duplicate by setting the T-flag in the
command header as described in [DIAMBASE] section 3.
This is the default behavior if the AVP isn't included in the
reply from the authorization server.
CONTINUE 1
When the Direct-Debiting-Failure-Handling AVP is set to CONTINUE
the service SHOULD be granted even if credit-control messages
can't be delivered and the request should be deleted.
8.16 Multiple-Services-Credit-Control AVP
Multiple-Services-Credit-Control AVP (AVP Code XXX - IANA please fill
in and remove this note - suggested value 456) is of type Grouped and
contains the AVPs related to the independent credit control of
multiple services feature. Note that each instance of this AVP
carries units related to one or more services or related to a single
rating-group.
The Service-Identifier and the Rating-Group AVPs are used to
associate the granted units to a given service or rating group.
In case both the Service-Identifier and the Rating-Group AVPs are
included, the target of the service units is always the service(s)
indicated by the value of the Service-Identifier AVP(s). If only the
Rating-Group-Id AVP is present, the Multiple-Services-Credit-Control
AVP relates to all the services that belong to the specified rating
group.
The G-S-U-Pool-Reference AVP allows the server to specify a G-S-U-
Pool-Identifier identifying a credit pool within which the units of
the specified type are considered to be pooled. If a G-S-U-Pool-
Reference AVP is present then actual service units of the specified
type MUST also be present. For example, if the G-S-U-Pool-Reference
AVP specifies Unit-Type TIME, then the CC-Time AVP MUST be present.
The Requested-Service-Unit AVP MAY contain the amount of requested
service units or the requested monetary value. It MUST be present in
the initial interrogation and within the intermediate interrogations
where new quota is requested. If the credit-control client does not
include the Requested-Service-Unit AVP in a request command, for
instance because it has determined that the end-user terminated the
service, the server MUST debit the used amount from the user's
account but MUST NOT return a new quota in the corresponding answer.
The Validity-Time, Result-Code and Final-Unit-Indication AVPs MAY be
present in an answer command as defined in section 5.1.1 and 5.6 for
the graceful service termination.
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When both the Tariff-Time-Change and Tariff-Change-Usage AVPs are
present, the server MUST include two separate instances of the
Multiple-Services-Credit-Control AVP with the Granted-Service-Unit
AVP associated to the same Service-Identifier and/or Rating-Group.
Where the two quotas are associated to the same pool or to different
pools, the credit pooling mechanism as defined in section 5.1.1
applies. The Tariff-Change-Usage AVP MUST NOT be included in request
commands, to report used units before and after tariff time change
the Used-Service-Unit AVP MUST be used.
A server not implementing the independent credit control of multiple
services functionality MUST treat the Multiple-Services-Credit-
Control AVP as invalid AVP.
The Multiple-Services-Control AVP has the following ABNF grammar:
Multiple-Services-Credit-Control ::= < AVP Header: TBD >
[ Granted-Service-Unit ]
[ Requested-Service-Unit ]
*[ Used-Service-Unit ]
[ Tariff-Change-Usage ]
*[ Service-Identifier ]
[ Rating-Group ]
*[ G-S-U-Pool-Reference ]
[ Validity-Time ]
[ Result-Code ]
[ Final-Unit-Indication ]
*[ AVP ]
8.17 Granted-Service-Unit AVP
Granted-Service-Unit AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 431) is of type Grouped and
contains the amount of units that the Diameter credit-control client
can provide to the end user until the service must be released or the
new Credit-Control-Request must be sent. A client is not required to
implement all of the unit types, and must treat unknown or
unsupported unit types in the answer message as an incorrect CCA
answer. In that case the client MUST terminate the credit control
session and indicate in the Termination-Cause AVP reason
DIAMETER_BAD_ANSWER.
The Granted-Service-Unit AVP has the following ABNF grammar:
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Granted-Service-Unit ::= < AVP Header: TBD >
[ Tariff-Time-Change ]
[ CC-Time ]
[ CC-Money ]
[ CC-Total-Octets ]
[ CC-Input-Octets ]
[ CC-Output-Octets ]
[ CC-Service-Specific-Units ]
*[ AVP ]
8.18 Requested-Service-Unit AVP
The Requested-Service-Unit AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 437) is of type Grouped and
contains the amount of requested units specified by the Diameter
credit-control client. A server is not required to implement all of
the unit types, and must treat unknown or unsupported unit types as
invalid AVPs.
The Requested-Service-Unit AVP has the following ABNF grammar:
Requested-Service-Unit ::= < AVP Header: TBD >
[ CC-Time ]
[ CC-Money ]
[ CC-Total-Octets ]
[ CC-Input-Octets ]
[ CC-Output-Octets ]
[ CC-Service-Specific-Units ]
*[ AVP ]
8.19 Used-Service-Unit AVP
The Used-Service-Unit AVP is of type Grouped AVP (AVP Code XXX - IANA
please fill in and remove this note - suggested value 446) and
contains the amount of used units measured from the point when the
service became active or, in case of interim interrogations are used
during the session, from the point when the previous measurement
ended.
The Used-Service-Unit AVP has the following ABNF grammar:
Used-Service-Unit ::= < AVP Header: TBD >
[ Tariff-Change-Usage ]
[ CC-Time ]
[ CC-Money ]
[ CC-Total-Octets ]
[ CC-Input-Octets ]
[ CC-Output-Octets ]
[ CC-Service-Specific-Units ]
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*[ AVP ]
8.20 Tariff-Time-Change AVP
The Tariff-Time-Change AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 451) is of type Time, it is sent
from the server to the client and includes the time in seconds since
January 1, 1900 00:00 UTC when the tariff of the service will be
changed.
The tariff change mechanism is optional for client and server and it
is not used for time-based services as defined in the section 5.
If a client does not support the tariff time change mechanism it MUST
treat Tariff-Time-Change AVP in the answer message as an incorrect
CCA answer. In that case the client terminates the credit control
session and indicate in the Termination-Cause AVP reason
DIAMETER_BAD_ANSWER.
Omission of this AVP means that no tariff change is to be reported.
8.21 CC-Time AVP
The CC-Time AVP (AVP Code XXX - IANA please fill in and remove this
note - suggested value 420) is of type Unsigned32, and indicates the
length of the requested, granted or used time in seconds.
8.22 CC-Money AVP
The CC-Money AVP (AVP Code XXX - IANA please fill in and remove this
note - suggested value 413) is of type Grouped, and specifies the
monetary amount in the given currency. The Currency-Code AVP SHOULD
be included. It has the following ABNF grammar:
CC-Money ::= < AVP Header: TBD >
{ Unit-Value }
[ Currency-Code ]
8.23 CC-Total-Octets AVP
The CC-Total-Octets AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 421) is of type Unsigned64, and
contains the total number of requested, granted or used octets
regardless of the direction (sent or received).
8.24 CC-Input-Octets AVP
The CC-Input-Octets AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 412) is of type Unsigned64, and
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contains the number of requested, granted or used octets that can
be/have been received from the end user.
8.25 CC-Output-Octets AVP
The CC-Output-Octets AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 414) is of type Unsigned64, and
contains the number of requested, granted or used octets that can
be/have been sent to the end user.
8.26 CC-Service-Specific-Units AVP
The CC-Service-Specific-Units AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 417) is of type Unsigned64,
and specifies the number of service specific units (e.g. number of
events, points) given in a selected service. The service specific
units always refer to the service identified in the Service-
Identifier AVP (or Rating-Group AVP when the Multiple-Services-
Credit-Control AVP is used).
8.27 Tariff-Change-Usage AVP
The Tariff-Change-Usage AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 452) is of type Enumerated and
defines whether units are used before or, after a tariff change, or
the units straddled tariff change when a tariff change has occurred
during the reporting period.
Omission of this AVP means that no tariff change has occurred.
In addition, when present in answer messages as part of the Multiple-
Services-Credit-Control AVP, this AVP defines whether units are
allocated to be used before or after a tariff change event.
Omission of this AVP in answer messages when the Tariff-Time-Change
AVP is present means that the single quota mechanism applies.
Tariff-Change-Usage can be one of the following:
UNIT_BEFORE_TARIFF_CHANGE 0
When present in the Multiple-Services-Credit-Control AVP, this
value indicates the amount of the units allocated for use before a
tariff change occurs.
When present in the Used-Service-Unit AVP, this value indicates
the amount of resource units used before a tariff change had
occurred.
UNIT_AFTER_TARIFF_CHANGE 1
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When present in the Multiple-Services-Credit-Control AVP, this
value indicates the amount of the units allocated for use after a
tariff change occurs.
When present in the Used-Service-Unit AVP, this value indicates
the amount of resource units used after tariff change had
occurred.
UNIT_INDETERMINATE 2
The used unit contains the amount of units that straddle the
tariff change (e.g. the metering process reports to the credit-
control client in blocks of n octets and one block straddled the
tariff change). This value is to be used only in the Used-Service-
Unit AVP.
8.28 Service-Identifier AVP
The Service-Identifier AVP is of type UTF8String (AVP Code XXX - IANA
please fill in and remove this note - suggested value 439) and
contains a unique identifier of a service. This is an identifier
allocated by the service provider, by the service element
manufacturer or by a standardization body and MUST uniquely identify
a given service. The format of the service identifier is:
"service-identifier" "@" "domain"
service-identifier = Token
The Token is an arbitrary string of characters
and digits.
domain = represents the entity that allocated the service-identifier.
It can be ietf.org, 3gpp.org etc. if the identifier is
allocated by a standardization body, or it can be the FQDN
of the service provider (e.g. provider.example.com) or of
the vendor (e.g. vendor.example.com) if the identifier is
allocated by a private entity.
Services that are for private use only, i.e. to one provider's own
use, where no interoperability is deemed useful may define private
identifiers without need of coordination. However, when
interoperability is wanted, coordination of the identifiers via e.g.
publication of informational RFC is RECOMMENDED to make Service-
Identifier globally available.
A usage example of this AVP for multiple services in one user session
is illustrated in Appendix A (Flow IX).
8.29 Rating-Group AVP
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The Rating-Group AVP is of type Unsigned32 (AVP Code XXX - IANA
please fill in and remove this note - suggested value 432) and
contains the identifier of a rating group. All the services subject
to the same rating type are part of the same rating group. This is an
identifier allocated by the home service provider and MUST be unique
within the home service provider domain.
A usage example of this AVP is illustrated in Appendix A (Flow IX).
8.30 G-S-U-Pool-Reference AVP
The G-S-U-Pool-Reference AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 457) is of type Grouped, it is
used in the Credit-Control-Answer message and associates the Granted-
Service-Units AVP within which it appears with a credit pool within
the session.
The G-S-U-Pool-Identifier AVP specifies the credit pool from which
credit is drawn for this unit type.
The CC-Unit-Type AVP specifies the type of units for which credit is
pooled.
The Unit-Value AVP specifies the multiplier, which converts between
service units of type CC-Unit-Type and abstract service units within
the credit pool (and hence to service units of any other service or
rating group associated with the same pool).
The G-S-U-Pool-Reference AVP has the following ABNF grammar:
G-S-U-Pool-Reference ::= < AVP Header: TBD >
{ G-S-U-Pool-Identifier }
{ CC-Unit-Type }
{ Unit-Value }
8.31 G-S-U-Pool-Identifier AVP
The G-S-U-Pool-Identifier AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 453) is of type Unsigned32 and
identifies a 'credit pool' within the session.
8.32 CC-Unit-Type AVP
The CC-Unit-Type AVP (AVP Code XXX - IANA please fill in and remove
this note - suggested value 454) is of type Enumerated and specifies
the type of units which are considered to be pooled into a credit
pool.
The following values are defined for the CC-Unit-Type AVP:
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TIME 0
MONEY 1
TOTAL-OCTETS 2
INPUT-OCTETS 3
OUTPUT-OCTETS 4
SERVICE-SPECIFIC-UNITS 5
8.33 Validity-Time AVP
The Validity-Time AVP is of type Unsigned32 (AVP Code XXX - IANA
please fill in and remove this note - suggested value 448) and it is
sent from the credit-control server to the credit-control client. The
AVP contains the validity time of the granted service units. The
measurement of the Validity-Time is started at reception of the
Credit-Control-Answer Message containing this AVP. If the granted
service units have not been consumed within the validity time
specified in this AVP, the credit-control client MUST send a Credit-
Control-Request message to the server with CC-Request-Type set to
UPDATE_REQUEST. The value field of the Validity-Time AVP is given in
seconds.
The Validity-Time AVP is also used for the graceful service
termination (see section 5.6) to indicate to the credit control
client how long the subscriber is allowed to use network resources
after the specified action (i.e. REDIRECT or RESTRICT_ACCESS)
started. Upon the Validity-Time elapses a new intermediate
interrogation is sent to the server.
8.34 Final-Unit-Indication AVP
The Final-Unit-Indication AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 430) is of type Grouped and
indicates that the Granted-Service-Unit AVP in the Credit-Control-
Answer, or in the AA answer, contains the final units for the
service. After these units have expired, the Diameter credit-control
client is responsible for executing the action indicated in the
Final-Unit-Action AVP (see section 5.6).
If more than one unit types are received in the Credit-Control-
Answer, the Unit type which first expired SHOULD cause the credit-
control client to execute the specified action.
In the first interrogation, the Final-Unit-Indication AVP with Final-
Unit-Action REDIRECT or RESTRICT_ACCESS can also be present with no
Granted-Service-Unit AVP in the Credit-Control-Answer or in the AA
answer. This indicates to the Diameter credit-control client to
immediately execute the specified action. If the home service
provider policy is to terminate the service, naturally, the server
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SHOULD return the appropriate transient failure (see section 9.1) in
order to implement the policy-defined action.
The Final-Unit-Action AVP defines the behavior of the service element
when the user's account cannot cover the cost of the service and MUST
always be present if the Final-Unit-Indication AVP is included in a
command.
If the Final-Unit-Action AVP is set to TERMINATE no other AVPs MUST
be present.
If the Final-Unit-Action AVP is set to REDIRECT at least the
Redirect-Server AVP MUST be present. The Restriction-Filter-Rule AVP
or the Filter-Id AVP MAY be present in the Credit-Control-Answer
message if the user is allowed to access also other services not
accessible through the address given in the Redirect-Server AVP.
If the Final-Unit-Action AVP is set to RESTRICT_ACCESS either the
Restriction-Filter-Rule AVP or the Filter-Id AVP SHOULD be present.
The Filter-Id AVP is defined in [NASREQ]. The Filter-Id AVP can be
used to reference an IP filter list installed in the access device by
other means than the Diameter Credit Control Application e.g. locally
configured or configured by another entity.
The Final-Unit-Indication AVP has the following ABNF grammar:
Final-Unit-Indication ::= < AVP Header: TBD >
{ Final-Unit-Action }
*[ Restriction-Filter-Rule ]
*[ Filter-Id ]
[ Redirect-Server ]
8.35 Final-Unit-Action AVP
The Final-Unit-Action AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 449) is of type Enumerated and
indicates to the credit-control client the action to be taken when
the user's account cannot cover the service cost.
The Final-Unit-Action can be one of the following:
TERMINATE 0
The credit control client MUST terminate the service session. This
is the default handling applicable whenever the credit control
client receives an unsupported Final-Unit-Action value and MUST be
supported by all the Diameter credit control client
implementations conforming to this specification.
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REDIRECT 1
The service element MUST redirect the user to the address
specified in the Redirect-Server-Address AVP. The redirect action
is defined in section 5.6.2.
RESTRICT_ACCESS 2
The access device MUST restrict the user access according to the
IP packet filters defined in the Restriction-Filter-Rule AVP or
according to the IP packet filters identified by the Filter-Id
AVP. All the packets not matching the filters MUST be dropped (see
section 5.6.3).
8.36 Restriction-Filter-Rule AVP
The Restriction-Filter-Rule AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 438) is of type IPFilterRule
and provides filter rules corresponding to services which are to
remain accessible despite there being no more service units granted.
The access device need to configure the specified filter rules for
the subscriber and MUST drop all the packets not matching these
filters. Zero, one or more such AVPs MAY be present in a Credit-
Control-Answer message or in an AA answer message.
8.37 Redirect-Server AVP
The Redirect-Server AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 434) is of type Grouped and
contains the address information of the redirect server (e.g. HTTP
redirect server, SIP Server) where the end user is to be connected
when the account cannot cover the service cost. It MUST be present
when the Final-Unit-Action AVP is set to REDIRECT.
It has the following ABNF grammar:
Redirect-Server ::= < AVP Header: TBD >
{ Redirect-Address-Type }
{ Redirect-Server-Address }
8.38 Redirect-Address-Type AVP
The Redirect-Address-Type AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 433) is of type Enumerated and
defines the address type of the address given in the Redirect-Server-
Address AVP.
The address type can be one of the following:
IPv4 Address 0
The address type is in form of "dotted-decimal" IPv4 address,
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as defined in [IPv4].
IPv6 Address 1
The address type is in form of IPv6 address, as defined in
[IPv6Addr]. The address is a text representation of the address
in either the preferred or alternate text form [IPv6Addr].
Conformant implementations MUST support the preferred form and
SHOULD support the alternate text form for IPv6 addresses.
URL 2
The address type is in form of Uniform Resource Locator, as
defined in [URL].
SIP URI 3
The address type is in form of SIP Uniform Resource Indicator, as
defined in [SIP].
8.39 Redirect-Server-Address AVP
The Redirect-Server-Address AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 435) is of type UTF8String and
defines the address of the redirect server (e.g. HTTP redirect
server, SIP Server) where the end user is to be connected when the
account cannot cover the service cost.
8.40 Multiple-Services-Indicator AVP
The Multiple-Services-Indicator AVP (AVP Code XXX - IANA please fill
in and remove this note - suggested value 455) is of type Enumerated
and indicates whether the Diameter Credit-control client is capable
of handling multiple services independently within a (sub-) session.
The absence of this AVP means that independent credit control of
multiple services is not supported.
A server not implementing the independent credit control of multiple
services MUST treat the Multiple-Services-Indicator AVP as invalid
AVP.
The following values are defined for the Multiple-Services-Indicator
AVP:
MULTIPLE_SERVICES_NOT_SUPPORTED 0
Client does not support independent credit control of multiple
services within a (sub-)session.
MULTIPLE_SERVICES_SUPPORTED 1
Client supports independent credit control of multiple services
within a (sub-)session.
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8.41 Requested-Action AVP
The Requested-Action AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 436) is type of Enumerated and
contains the requested action being sent by Credit-Control-Request
command where the CC-Request-Type is set to EVENT_REQUEST. The
following values are defined for the Requested-Action AVP:
DIRECT_DEBITING 0
Direct debiting indicates that the request is to decrease the end
user's account according to information specified in the
Requested-Service-Unit AVP and/or Service-Identifier AVP
(additional rating information may be included in service specific
AVPs or in the Service-Parameter-Info AVP). The Granted-Service
Unit AVP in the Credit-Control-Answer command contains the debited
units.
REFUND_ACCOUNT 1
Refund account indicates that the request is to increase the end
user's account according to information specified in the
Requested-Service-Unit AVP and/or Service-Identifier AVP
(additional rating information may be included in service specific
AVPs or in the Service-Parameter-Info AVP). The Granted-Service
Unit AVP in the Credit-Control-Answer command contains the
refunded units.
CHECK_BALANCE 2
Check balance indicates that the request is a balance check
request. In this case the checking of the account balance is done
without any credit reservation from the account. The Check-
Balance-Result AVP in the Credit-Control-Answer command contains
the result of the Balance Check.
PRICE_ENQUIRY 3
Price Enquiry indicates that the request is a price enquiry
request. In this case neither checking of the account balance nor
reservation from the account will be done, only the price of the
service will be returned in the Cost-Information AVP in the
Credit-Control-Answer Command.
8.42 Service-Parameter-Info AVP
The Service-Parameter-Info AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 440) is of type Grouped and
contains a service specific information used for price calculation or
rating. The Service-Parameter-Type AVP defines the service parameter
type and the Service-Parameter-Value AVP contains the parameter
value. The actual contents of these AVPs are not within the scope of
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this document and SHOULD be defined in another Diameter application,
standards written by other standardization bodies, or service
specific documentation.
In case of unknown service request (e.g. unknown Service-Parameter-
Type), the corresponding answer message MUST contain error code
DIAMETER_RATING_FAILED. A Credit Control Answer message with this
error MUST contain one or more Failed-AVP AVPs containing the
Service-Parameter-Info AVPs that caused the failure.
It has the following ABNF grammar:
Service-Parameter-Info ::= < AVP Header: TBD >
[ Service-Parameter-Type ]
[ Service-Parameter-Value ]
8.43 Service-Parameter-Type AVP
The Service-Parameter-Type AVP is of type Unsigned32 (AVP Code XXX -
IANA please fill in and remove this note - suggested value 441) and
defines the type of the service event specific parameter (e.g. it can
be end-user location, service name). The different parameters and
their types are service specific and the meanings of these parameters
are not defined in this document. The one who allocates the Service-
Identifier, i.e. unique identifier of a service, is also responsible
for assigning Service-Parameter-Type values for the service and
ensuring their uniqueness within the given service. The Service-
Parameter-Value AVP contains the value associated with the service
parameter type.
8.44 Service-Parameter-Value AVP
The Service-Parameter-Value AVP is of type OctetString (AVP Code XXX
- IANA please fill in and remove this note - suggested value 442) and
contains the value of the service parameter type.
8.45 Subscription-Id AVP
The Subscription-Id AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 443) is used to identify the end
user's subscription and is of type Grouped. The Subscription-Id AVP
includes a Subscription-Id-Data AVP that hold the identifier and a
Subscription-Id-Type AVP that defines the identifier type.
It has the following ABNF grammar:
Subscription-Id ::= < AVP Header: TBD >
{ Subscription-Id-Type }
{ Subscription-Id-Data }
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8.46 Subscription-Id-Type AVP
The Subscription-Id-Type AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 450) is of type Enumerated and it
is used to determine which type of identifier that is carried by the
Subscription-Id AVP. A server is not required to implement all of the
Subscription-Id-Types, and MUST treat unknown or unsupported
Subscription-Id-Types as invalid AVP values.
The identifier can be one of the following:
END_USER_E164 0
The identifier is in international E.164 format (e.g. MSISDN),
according to the ITU-T E.164 numbering plan as defined in [E164]
and [CE164].
END_USER_IMSI 1
The identifier is in international IMSI format, according to the
ITU-T E.212 numbering plan as defined in [E121] and [CE121].
END_USER_SIP_URI 2
The identifier is in the form of a SIP URL as defined in [SIP].
END_USER_NAI 3
The identifier is in the form of a Network Access Identifier as
defined in [NAI].
END_USER_PRIVATE 4
The Identifier is a credit-control server private identifier.
8.47 Subscription-Id-Data AVP
The Subscription-Id-Data AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 444) is used to identify the end-
user and is of type UTF8String. The Subscription-Id-Type AVP defines
which type of identifier is used.
8.48 User-Equipment-Info AVP
The User-Equipment-Info AVP (AVP Code XXX - IANA please fill in and
remove this note - suggested value 458) is of type Grouped, and
allows the Credit-control client to indicate the identity and
capability of the terminal the subscriber is using for the connection
to network.
It has the following ABNF grammar:
User-Equipment-Info ::= < AVP Header: TBD >
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{ User-Equipment-Info-Type }
{ User-Equipment-Info-Value }
8.49 User-Equipment-Info-Type AVP
The User-Equipment-Info-Type AVP is of type Enumerated (AVP Code XXX
- IANA please fill in and remove this note - suggested value 459) and
defines the type of the user equipment information contained in the
User-Equipment-Info-Value AVP.
The identifier can be one of the following:
IMEISV 0
The identifier contains the International Mobile Equipment
Identifier and Software Version in the international IMEISV format
according to 3GPP TS 23.003 [3GPPIMEI].
MAC 1
The 48-bit MAC address is formatted as described in [RAD802.1X].
EUI64 2
The 64-bit identifier used to identify hardware instance of the
product as defined in [EUI64].
MODIFIED_EUI64 3
There are a number of types of terminals that have identifiers
other than IMEI, IEEE 802 MACs or EUI-64. These identifiers can be
converted to modified EUI-64 format as described in [IPv6Addr] or
using some other methods referred to in the service specific
documentation.
8.50 User-Equipment-Info-Value AVP
The User-Equipment-Info-Value AVP (AVP Code XXX - IANA please fill in
and remove this note - suggested value 460) is of type OctetString
The User-Equipment-Info-Type AVP defines which type of identifier is
used.
9. Result Code AVP values
This section defines new Result-Code AVP [DIAMBASE] values that must
be supported by all Diameter implementations that conform to this
specification.
The Credit-Control-Answer message includes the Result-Code AVP, which
may indicate that an error was present in the Credit-Control-Request
message. A rejected Credit-Control-Request message SHOULD cause the
user's session to be terminated.
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9.1 Transient Failures
Errors that fall within the transient failures category are used to
inform a peer that the request could not be satisfied at the time it
was received, but MAY be able to satisfy the request in the future.
DIAMETER_END_USER_SERVICE_DENIED 4010
The credit-control server denies the service request due to
service restrictions. If the CCR contained used-service-units they
are deducted, if possible.
DIAMETER_CREDIT_CONTROL_NOT_APPLICABLE 4011
The credit-control server determines that the service can be
granted to the end user but no further credit-control is needed
for the service (e.g. service is free of charge).
DIAMETER_CREDIT_LIMIT_REACHED 4012
The credit-control server denies the service request since the
end-
user's account could not cover the requested service. If the CCR
contained used-service-units they are deducted, if possible.
9.2 Permanent Failures
Errors that fall within permanent failure category are used to inform
the peer that the request failed, and should not be attempted again.
DIAMETER_USER_UNKNOWN 5030
The specified end user is unknown in the credit-control server.
DIAMETER_RATING_FAILED 5031
This error code is used to inform the credit-control client that
the credit-control server cannot rate the service request due to
insufficient rating input, incorrect AVP combination or due to an
AVP or an AVP value that is not recognized or supported in the
rating. The Failed-AVP AVP MUST be included and contain a copy of
the entire AVP(s) that could not be processed successfully or an
example of the missing AVP complete with the Vendor-Id if
applicable. The value field of the missing AVP should be of
correct minimum length and contain zeroes.
10. AVP Occurrence Table
The following table presents the AVPs defined in this document, and
specifies in which Diameter messages they MAY, or MAY NOT be present.
Note that AVPs that can only be present within a Grouped AVP are not
represented in this table.
The table uses the following symbols:
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0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the
message. It is considered an error if there are more than
once instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.
10.1 Credit Control AVP Table
The table in this section is used to represent which Credit-control
applications specific AVPs defined in this document are to be present
in the Credit Control messages.
+-----------+
| Command |
| Code |
|-----+-----+
Attribute Name | CCR | CCA |
------------------------------|-----+-----+
Acct-Multi-Session-Id | 0-1 | 0-1 |
Auth-Application-Id | 1 | 1 |
CC-Correlation-Id | 0-1 | 0 |
CC-Session-Failover | 0 | 0-1 |
CC-Request-Number | 1 | 1 |
CC-Request-Type | 1 | 1 |
CC-Sub-Session-Id | 0-1 | 0-1 |
Check-Balance-Result | 0 | 0-1 |
Cost-Information | 0 | 0-1 |
Credit-Control-Failure- | 0 | 0-1 |
Handling | | |
Destination-Host | 0-1 | 0 |
Destination-Realm | 1 | 0 |
Direct-Debiting-Failure- | 0 | 0-1 |
Handling | | |
Event-Timestamp | 0-1 | 0-1 |
Final-Unit-Indication | 0 | 0-1 |
Granted-Service-Unit | 0 | 0-1 |
Multiple-Services-Credit- | 0+ | 0+ |
Control | | |
Multiple-Services-Indicator | 0-1 | 0 |
Origin-Host | 1 | 1 |
Origin-Realm | 1 | 1 |
Origin-State-Id | 0-1 | 0-1 |
Proxy-Info | 0+ | 0+ |
Redirect-Host | 0 | 0+ |
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Redirect-Host-Usage | 0 | 0-1 |
Redirect-Max-Cache-Time | 0 | 0–1 |
Requested-Action | 0-1 | 0 |
Requested-Service-Unit | 0-1 | 0 |
Route-Record | 0+ | 0+ |
Result-Code | 0 | 1 |
Service-Identifier | 0-1 | 0 |
Service-Parameter-Info | 0+ | 0 |
Session-Id | 1 | 1 |
Subscription-Id | 0+ | 0+ |
Termination-Cause | 0-1 | 0 |
User-Equipment-Info | 0-1 | 0 |
Used-Service-Unit | 0+ | 0 |
User-Name | 0-1 | 0-1 |
Validity-Time | 0 | 0-1 |
------------------------------|-----+-----+
10.2 Re-Auth-Request/Answer AVP Table
This section defines AVPs that are specific to Diameter Credit
Control Application and MAY be included in the Diameter Re-Auth-
Request/Answer (RAR/RAA) message [DIAMBASE].
Re-Auth-Request/Answer command MAY include the following additional
AVPs:
+---------------+
| Command Code |
|-------+-------+
Attribute Name | RAR | RAA |
------------------------------+-------+-------+
CC-Sub-Session-Id | 0-1 | 0-1 |
G-S-U-Pool-Identifier | 0-1 | 0-1 |
Service-Identifier | 0-1 | 0-1 |
Rating-Group | 0-1 | 0-1 |
------------------------------+-------+-------+
11. RADIUS/Diameter Credit-control Interworking Model
This section defines the basic principles for the Diameter Credit-
control/RADIUS prepaid inter-working model, that is a message
translation between RADIUS based prepaid solution and Diameter
Credit-control application. A complete description of the protocol
translations between RADIUS and Diameter Credit-control application
is
beyond the scope of this specification and SHOULD be addressed in
another appropriate document such as the RADIUS prepaid
specification.
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The Diameter credit-control architecture may have a Translation
Agent, which is capable of translation between RADIUS prepaid and
Diameter Credit-control protocol. An AAA server, usually the home AAA
server, may act as a Translation Agent while acting also as Diameter
credit-control client for service elements that use credit control
mechanisms other than Diameter credit-control, for instance RADIUS
prepaid. In this case the home AAA server contacts the Diameter
credit-control server as part of the authorization process. The
interworking architecture is illustrated in figure 7 and interworking
flow in figure 8. In roaming situation the service element (e.g. the
NAS) may be located in the visited network and a visited AAA server
is usually contacted. The visited AAA server connects then to the
home AAA server.
Radius prepaid
+--------+ +---------+ protocol +------------+ +--------+
| End |<----->| Service |<---------->| Home AAA | |Business|
| User | | Element | | Server | |Support |
+--------+ +-->| | |+----------+|->|System |
| +---------+ ||CC client || | |
| |+----------+| | |
+--------+ | +------^-----+ +----^---+
| End |<--+ credit-control | |
| User | protocol | |
+--------+ +-------V--------+ |
|Credit-control |----+
| Server |
+----------------+
Figure 7: Credit-control architecture with Service Element
containing translation agent, translating RADIUS
prepaid to Diameter credit control protocol
When the AAA server acting as a Translation Agent receives an initial
RADIUS Access-Request message from service Element (e.g. NAS access),
it performs regular Authentication and Authorization. If the RADIUS
Access-Request message indicates that the service element is capable
of credit-control, and if the home AAA server finds that the
subscriber is a prepaid subscriber then a Diameter Credit control
request SHOULD be sent towards the credit-control server to perform
credit authorization and to establish a credit control session. After
the Diameter credit-control server checks the end user's account
balance, rates the service and reserves credit from the end user's
account, the reserved quota is returned to the home AAA server in the
Diameter Credit-Control-Answer. Then the home AAA server sends the
reserved quota to the service element in the RADIUS Access-Accept.
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At the expiry of the allocated quota, the service element sends a new
RADIUS Access-Request to the home AAA server containing the units
used this far. The home AAA server shall map RADIUS Access-Request
containing the reported units to the Diameter credit-control server
in a Diameter Credit-Control-Request (UPDATE_REQUEST). The Diameter
credit-control server debits the used units from the end user's
account and allocates a new quota that is returned to the home AAA
server in the Diameter Credit-Control-Answer. The quota is
transferred to the service element in the RADIUS Access-Accept. When
the end user terminates the service or when the entire quota has been
used, the service element sends a RADIUS Access-Request. To debit the
used units from the end user's account and to stop the credit control
session, the home AAA server sends a Diameter Credit-Control-Request
(TERMINATION_REQUEST) to the credit-control server. The Diameter
credit-control server acknowledges the session termination by sending
a Diameter Credit-Control-Answer to the home AAA server. The RADIUS
Access-Accept is sent to the NAS.
A following diagram illustrates a RADIUS prepaid - Diameter credit
control interworking sequence.
Service Element Translation agent
(e.g.NAS) (CC Client) CC Server
| Access-Request | |
|----------------------->| |
| | CCR (initial) |
| |----------------------->|
| | CCA (granted_Units) |
| |<-----------------------|
| Access-Accept | |
| (granted Units) | |
|<-----------------------| |
: : :
| Access-Request | |
| (used Units) | |
|----------------------->| |
| | CCR (update, |
| | used Units, |
| |----------------------->|
| | CCA (granted_Units) |
| |<-----------------------|
| Access-Accept | |
| (granted Units) | |
|<-----------------------| |
: : :
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| Access-Request | |
|----------------------->| |
| | CCR (termin., |
| | used Units) |
| |----------------------->|
| | CCA |
| |<-----------------------|
| Access-Accept | |
|<-----------------------| |
| | |
Figure 8: Message flow example with RADIUS prepaid - Diameter
credit control interworking
12. IANA Considerations
This section contains the namespaces that have either been created in
this specification, or the values assigned to existing namespaces
managed by IANA.
12.1 Application Identifier
This specification assigns the value XXX [IANA please fill in XXX
(suggested value 4) and remove this note] to the Application
Identifier namespace defined in [DIAMBASE]. See section 1.3 for more
information.
12.2 Command Codes
This specification uses the value [IANA please fill in XXX (suggested
value 272) and remove this note] from the Command code namespace
defined in [DIAMBASE].
12.3 AVP Codes
This specification assigns the values XXX - YYY [IANA please fill in
XXX, YYY (suggested values 411, 457) and remove this note] from the
AVP code namespace defined in [DIAMBASE] See section 8 for the
assignment of the namespace in this specification.
12.4 Result-Code AVP Values
This specification assigns the values X1, X2, X3, X4, X5 [IANA please
fill in XXX (suggested value 4010, 4011, 4012, 5030 and 5031) and
remove this note] from the Result-Code AVP value namespace defined in
[DIAMBASE]. See section 9 for the assignment of the namespace in this
specification.
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12.5 CC-Request-Type AVP
As defined in section 8.3, the CC-Request-Type AVP defines the values
X1-X3 [IANA please fill in X1-X3 (suggested value 1, 3) and remove
this note]. All remaining values are available for assignment via
Designated Expert [IANA].
12.6 CC-Session-Failover AVP
As defined in section 8.4, the CC-Failover-Supported AVP defines the
values X1-X2 [IANA please fill in X1, X2 (suggested value 0, 1) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.7 CC-Unit-Type AVP
As defined in section 8.32, the CC-Unit-Type AVP defines the values
X1-X5 [IANA please fill in X1-X5 (suggested value 0, 5) and remove
this note]. All remaining values are available for assignment via
Designated Expert [IANA].
12.8 Check-Balance-Result AVP
As defined in Section 8.6, the Check-Balance-Result AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 1) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.9 Credit-Control AVP
As defined in section 8.13, the Credit-Control AVP defines the values
X1-X2 [IANA please fill in X1-X2 (suggested value 0, 1) and remove
this note]. All remaining values are available for assignment via
Designated Expert [IANA].
12.10 Credit-Control-Failure-Handling AVP
As defined in Section 8.14, the Credit-Control-Failure-Handling AVP
defines the values [IANA please fill in X1-X2 (suggested value 0, 2)
and remove this note]. All remaining values are available for
assignment via Designated Expert [IANA].
12.11 Direct-Debiting-Failure-Handling AVP
As defined in Section 8.15, the Direct-Debiting-Failure-Handling AVP
defines the values [IANA please fill in X1-X2 (suggested value 0, 1)
and remove this note]. All remaining values are available for
assignment via Designated Expert [IANA].
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12.12 Final-Unit-Action AVP
As defined in Section 8.35, the Final-Unit-Action AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 2) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.13 Multiple-Services-Indicator AVP
As defined in Section 8.40, the Multiple-Services-Indicator AVP
defines the values X1-X2 [IANA please fill in X1-X2 (suggested value
0, 1) and remove this note]. All remaining values are available for
assignment via Designated Expert [IANA].
12.14 Redirect-Address-Type AVP
As defined in Section 8.38, the Redirect-Address-Type AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 3) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.15 Requested-Action AVP
As defined in Section 8.41, the Requested-Action AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 3) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.16 Subscription-Id-Type AVP
As defined in Section 8.46, the Subscription-Id-Type AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 4) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.17 Tariff-Change-Usage AVP
As defined in Section 8.27, the Tariff-Change-Usage AVP defines the
values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 2) and
remove this note]. All remaining values are available for assignment
via Designated Expert [IANA].
12.18 User-Equipment-Info-Type AVP
As defined in Section 8.49, the User-Equipment-Info-Type AVP defines
the values X1-X2 [IANA please fill in X1-X2 (suggested value 0, 3)
and remove this note]. All remaining values are available for
assignment via Designated Expert [IANA].
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13. Credit-control Application Related Parameters
Tx timer
When real-time credit-control is required, the credit-control
client contacts the credit-control server before and during the
service is provided to an end user. Due to real-time nature of the
application the communication delays SHOULD be minimized, e.g. to
avoid too long service set up time experienced by the end user.
The Tx timer is introduced to control the waiting time in the
client in the PENDING state. When the Tx timer elapses the credit-
control client takes an action to the end user according to the
value of the Credit-Control-Failure-Handling AVP or according to
the value of the Direct-Debiting-Failure-Handling AVP.
The recommended value is 10 seconds.
Tcc timer
The Tcc timer supervises an ongoing credit control session in the
credit control server. It is RECOMMENDED to use the Validity-Time
as input to set the Tcc timer value. To avoid the credit control
session in the Diameter credit control server to change to Idle
state in case of short transient network failure, Tcc MAY be set
to two times the value of Validity-Time.
Credit-Control-Failure-Handling and Direct-Debiting-Failure-Handling
Client implementations may offer the possibility to locally
configure these AVPs. In such a case their value and behavior is
defined in section 5.7 for the Credit-Control-Failure-Handling and
in section 6.5 for the Direct-Debiting-Failure-Handling.
14. Security Consideration
The Diameter base protocol [DIAMBASE] requires that each Diameter
implementation uses underlying security, i.e. IPsec or TLS. These
mechanisms are believed to provide sufficient protection under the
normal Internet threat model - that is, assuming the authorized nodes
engaging in the protocol have not been compromised, but the attacker
has complete control over the communication channels between them.
This includes eavesdropping, message modification, insertion, man-in-
the-middle and replay attacks. Note also that this application
includes a mechanism for application layer replay protection by the
means of Session-ID from [DIAMBASE], and CC-Request-Number specified
in this document. The Diameter credit control application is often
used within one domain and there may be just single hop between the
peers. In these environments the use of TLS or IPsec is sufficient.
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The details of TLS and IPsec related security considerations are
discussed in the [DIAMBASE].
Because this application handles monetary transactions (directly or
indirectly) this kind of application increases the interest for
various security attacks. Therefore all parties communicating with
each other MUST be authenticated, including, for instance, TLS
client-side authentication. In addition to this, authorization of the
client SHOULD be emphasized, i.e. that the client is allowed to
perform credit control for a certain user. The specific means of
authorization are outside of the scope of this specification but can
be for instance, manual configuration.
Another kind of threat is malicious modification, injection or
deletion of AVPs or complete credit control messages. The credit
control messages contain sensitive billing related information (such
as subscription Id, granted units, used units, cost information)
whose malicious modification can have financial consequences.
Sometimes simply delaying the credit control messages can cause
disturbances in the credit control client or server.
Even without any modification to the messages an adversary can invite
a security threat by eavesdropping, because the transactions contain
private information about the user. Also by monitoring the credit
control messages one can collect information about credit control
server's billing models and business relationships.
When third party relays or proxy are involved, the hop-by-hop
security does not necessarily provide sufficient protection for
Diameter user session. Diameter messages, such as CCR and CCA,
containing sensitive AVPs may be inappropriate in some cases to be
sent via untrusted Diameter proxy agents since there are no assurance
that third party proxies will not modify the credit control commands
or AVP values.
14.1 Direct Connection with Redirects
A Diameter Credit control agent cannot always know whether agents
between it and the end user's Diameter credit control server are
reliable. In this case the Diameter Credit control agent doesn't have
a routing entry in its Diameter Routing Table (defined in [DIAMBASE]
in section 2.7) for the realm of the Credit Control Server in the end
user's home domain. The Diameter Credit control agent can have a
default route configured to a local Redirect agent and it re-directs
the CCR message to the redirect agent. The local Redirect agent then
returns a redirect notification (Result-code 3006,
DIAMETER_REDIRECT_INDICATION) to the Credit control agent, as well
Diameter Credit control Server(s) information (Redirect-Host AVP) and
information (Redirect-Host-Usage AVP) how to the routing entry
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resulting from the Redirect-Host is to be used. The Diameter credit
control agent then forwards the CCR message directly to one of the
hosts identified by the CCA message from the redirect agent. If the
value of the Redirect-Host-Usage AVP is unequal than zero all
following messages are sent to the host specified in the Redirect-
Host AVP until the time specified by the Redirect-Max-Cache-Time AVP
is expired.
There are some authorization issues even with redirects. There may be
attacks towards nodes that have been properly authorized, but abuse
their authorization or have been compromised. These issues are
discussed more widely in [DIAMEAP] section 8.
15. References
15.1 Normative
[DIAMBASE] P. Calhoun, J. Loughney, J. Arkko, E. Guttman, G. Zorn.
"Diameter Base Protocol", RFC 3588, September 2003.
[3GPPCHARG] 3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects, Service
aspects; Charging and Billing, (release 5), 3GPP TS
22.115 v. 5.2.1, 2002-03
[SIP] M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, G.
Camarillo, A. Johnston, J. Peterson, R. Sparks
"SIP: Session Initiation Protocol", RFC 3261. June 2002.
[NAI] Aboba, Beadles "The Network Access Identifier." RFC 2486.
January 1999.
[E164] Recommendation E.164/I.331 (05/97): The International
Public Telecommunication Numbering Plan. 1997.
[CE164] Complement to ITU-T Recommendation E.164 (05/1997):"List
of ITU-T Recommendation E.164 assigned country codes",
June 2000.
[E212] Recommendation E.212 (11/98): The international
identification plan for mobile terminals and mobile
users. 1998.
[CE212] Complement to ITU-T Recommendation E.212 (11/1997):" List
of mobile country or geographical area codes ", February
1999.
[IANA] Narten, Alvestrand, "Guidelines for Writing an IANA
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Diameter Credit Control Application May 14, 2004
Considerations Section in RFCs", BCP 26, RFC 2434,
October
1998
[IPv4] J. Postel. "Internet Protocol", STD 5, RFC 791, September
1981.
[IPv6Addr] R. Hinden, S. Deering. "Internet Protocol Version 6
(IPv6)
Addressing Architecture", RFC 3513, April 2003.
[KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[ISO4217] Codes for the representation of currencies and funds,
International Standard ISO 4217,2001
[NASREQ] P. Calhoun, G. Zorn, D. Spence, D. Mitton. "Diameter
NASREQ Application", IETF work in progress.
[AAATRANS] B. Aboba, J. Wood. "Authentication, Authorization and
Accounting (AAA) Transport Profile", RFC 3539, June 2003
[URL] T. Berners-Lee, L. Masinter, M. McCahill. "Uniform
Resource Locators (URL)", RFC 1738, December 1994
[RAD802.1X] P. Congdon, et.al "IEEE 802.1X RADIUS Usage Guidelines",
RFC 3580, September 2003.
[EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority",
http://standards.ieee.org/regauth/oui/tutorials/EUI64.htm
l March 1997.
[3GPPIMEI] 3rd Generation Partnership Project; Technical
Specification Group Core Network, Numbering, addressing
and identification, (release 5), 3GPP TS 23.003
v. 5.8.0, 2003-12
15.2 Non-Normative
[RFC2866] C. Rigney. "Radius Accounting", RFC 2866, June 2000
[DIAMMIP] P. Calhoun, T. Johansson, C. Perkins "Diameter Mobile IP
Application", IETF work in progress.
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Diameter Credit Control Application May 14, 2004
[RFC2865] C. Rigney, S. Willens, A. Rubens, W. Simpson. "Remote
Authentication Dial In User Service (RADIUS), RFC 2865,
June 2000
[DIAMEAP] P. Eronen, T. Hiller, G. Zorn. "Diameter Extensible
Authentication Protocol (EAP) Application", IETF work in
progress.
16. Acknowledgement
The authors would like to thank Bernard Aboba, Jari Arkko, Robert
Ekblad, Pasi Eronen, Benny Gustafsson, Robert Karlsson, Avi Lior,
Paco Marin, Jussi Maki, Jeff Meyer, Anne Narhi, John Prudhoe,
Christopher Richards, Juha Vallinen and Mark Watson for their
comments and suggestions.
Appendix A Credit Control sequences
A.1 Flow I
End-User NAS AAA Server CC Server
(CC Client)
|(1)User Logon |(2)AA Request (CC AVPs) |
|------------------>|------------------->| |
| | |(3)CCR(initial, CC AVPs)
| | |------------------->|
| | | (4)CCA(granted Units)
| | |<-------------------|
| |(5)AA Answer(granted Units) |
|(6)Access granted |<-------------------| |
|<----------------->| | |
| | | |
: : : :
| |(7)CCR(update,used Units) |
| |------------------->|(8)CCR |
(update,used units)
| | |------------------->|
| | |(9)CCA(granted Units)
| |(10)CCA(granted Units)<------------------|
| |<-------------------| |
: : : :
| (Auth. lifetime expires) | |
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| |(11) AAR (CC AVP) | |
| |------------------->| |
| | (12) AAA | |
| |<-------------------| |
: : : :
: : : :
|(13) User logoff | | |
|------------------>|(14)CCR(term.,used-Units) |
| |------------------->|(15)CCR |
| | | (term.,used-Units)
| | |------------------->|
| | | (16)CCA |
| | (17)CCA |<-------------------|
| |<-------------------| |
| |(18)STR | |
| |------------------->| |
| | (19)STA | |
| |<-------------------| |
Figure A.1: Flow I
A credit control flow for Network Access Services prepaid is shown in
Figure A.1. The Diameter [NASREQ] is implemented in the Network
Access Server (NAS). The focus of this flow is in the credit
authorization.
The user logs onto the network (1). The Diameter NAS first sends a
Diameter Authorization-Authentication-Request to the home Diameter
AAA Server, the credit-control client populates the AAR with the
Credit-Control AVP set to CREDIT_AUTHORIZATION and service specific
AVPs are included as usual [NASREQ]. The home Diameter AAA server
performs service specific Authentication and Authorization as usual.
The home Diameter AAA server determines that the user is a prepaid
user and notices from the Credit-Control AVP that the NAS has credit
control capabilities, it sends a Diameter Credit-Control-Request
with CC-Request-Type set to INITIAL_REQUEST to the Diameter credit-
control server to perform credit authorization (3) and to establish
a credit control session (the home Diameter AAA server may forward
service specific AVPs as received from the NAS as input for the
rating process). The Diameter credit-control server checks the end
user's account balance, rates the service and reserves credit from
the end user's account. The reserved quota is returned to the home
Diameter AAA server in the Diameter Credit-Control-Answer (4). The
home Diameter AAA server sends the reserved quota to the NAS in the
Diameter Authorization-Authentication-Answer. Upon successful AAA
the NAS starts the credit-control session and starts monitoring the
granted units (5). The NAS grant access to the end user (6). At the
expiry of the allocated quota, the NAS sends a Diameter Credit-
Control-Request with CC-Request-Type set to UPDATE_REQUEST to the
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Home Diameter AAA server (7). This message contains the units used
this far. The home Diameter AAA server forwards the CCR to the
Diameter credit-control server (8). The Diameter credit-control
server debits the used units from the end user's account and
allocates a new quota that is returned to the home Diameter AAA
server in the Diameter Credit-Control-Answer (9). The message is
forwarded to the NAS (10). During the ongoing credit-control session
the authorization-lifetime expires, the authorization/authentication
client in the NAS performs service specific re-authorization to the
home Diameter AAA server as usual. The credit-control client
populate the AAR with the Credit-Control AVP set to RE_AUTHORIZATION
indicating that the credit-control server shall not be contacted,
since the credit authorization is controlled by the burning rate of
the granted units (11). The home Diameter AAA server performs
service specific re-authorization as usual and returns the
Authorization-Authentication-Answer to the NAS (12). The end user
logs off from the network (13). To debit the used units from the end
user's account and to stop the credit control session, the NAS sends
a Diameter Credit-Control-Request with CC-Request-Type set to
TERMINATION_REQUEST to the home Diameter AAA server (14). The home
Diameter AAA server forwards the CCR to the credit-control server
(15). The Diameter credit-control server acknowledges the session
termination by sending a Diameter Credit-Control-Answer to the home
Diameter AAA server (16). The home Diameter AAA server forwards the
answer to the NAS (17). STR/STA take place between NAS and home
Diameter AAA server as usual (18-19).
A.2 Flow II
SIP Proxy/Registrar AAA
A (CC Client) Server B CC Server
|(i) REGISTER | | | |
|------------->|(ii) | | |
| |------------->| | |
| |authentication & | |
| |authorization | | |
| |<-------------| | |
|(iii)200 OK | | |
|<-------------| | |
: : : :
|(1) INVITE | :
|------------->|
| |(2) CCR (Intial, SIP specific AVP) |
| |------------------------------------------->|
| |(3) CCA (granted_Units) |
| |<-------------------------------------------|
| |(4) INVITE | |
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| |---------------------------->| |
: : : :
| |(5) CCR (update, used Units) |
| |------------------------------------------->|
| |(6) CCA (granted_Units) |
| |<-------------------------------------------|
: : : :
|(7) BYE | | |
|------------->| | |
| |(8) BYE | |
| |---------------------------->| |
| |(9) CCR (termination, used Units)----------|
| |------------------------------------------->|
| |(10) CCA () |
| |<-------------------------------------------|
| | | |
Figure A.2: Flow II
The end user (SIP User Agent A) sends REGISTER with credentials (i).
The SIP Proxy sends a request to the home AAA server to perform
Multimedia authentication and authorization by using for instance
Diameter Multimedia application (ii). The home AAA server checks that
the credentials are correct and checks the user profile. Eventually,
200 OK response (iii) is sent to the UA. Note that the Authentication
and Authorization is valid for the registration validity period
duration (i.e. until re-registration is performed), of several SIP
sessions may be established without re-authorization is performed.
UA A sends an INVITE (1). The SIP Proxy sends a Diameter Credit-
Control-Request (INITIAL_REQUEST) to the Diameter credit-control
server (2). The Credit-Control-Request contains information obtained
from the SIP signaling describing the requested service (e.g. calling
party, called party, Session Description Protocol attributes). The
Diameter credit-control server checks the end user's account balance,
rates the service and reserves credit from the end user's account.
The reserved quota is returned to the SIP Proxy in the Diameter
Credit-Control-Answer (3). The SIP Proxy forwards the SIP INVITE to
UA B (4). B's phone rings, and B answers. The media flows between
them and the SIP Proxy starts measuring the quota. At the expiry of
the allocated quota, the SIP Proxy sends a Diameter Credit-Control-
Request (UPDATE_REQUEST) to the Diameter credit-control server (5).
This message contains the units used this far. The Diameter credit-
control server debits the used units from the end user's account and
allocates new credit that is returned to the SIP Proxy in the
Diameter Credit-Control-Answer (6). The end user terminates the
service by sending a BYE (7). The SIP Proxy forwards the BYE message
to UA B (8) and sends a Diameter Credit-Control-Request
(TERMINATION_REQUEST) to the Credit-control server (9). The Diameter
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Credit-control server acknowledges the session termination by sending
a Diameter Credit-Control-Answer to the SIP Proxy (10).
A.3 Flow III
MMS Server
A (CC Client) B CC Server
|(1) Send MMS | | |
|--------------->| | |
| |(2) CCR (event, DIRECT_DEBITING,|
| | MMS specific AVP) |
| |-------------------------------->|
| |(3) CCA (granted_Units) |
| |<--------------------------------|
|(4) Send MMS Ack| | |
|<---------------| | |
| |(5) Notify MMS | |
| |--------------->| |
: : : :
| |(6) Retrieve MMS| |
| |<---------------| |
| |(7) Retrieve MMS| |
| | Ack | |
| |--------------->| |
| | | |
Figure A.3: Flow III
A credit control flow for Multimedia Messaging Services is shown in
Figure A.3. The sender is charged as soon as the messaging server
successfully stores the message.
The end user A sends a Multimedia Message (MMS) to the MMS Server
(1). The MMS Server stores the message and sends a Diameter Credit-
Control-Request (EVENT_REQUEST with Requested-Action:
DIRECT_DEBITING) to the Diameter credit-control server (2). The
Credit-Control-Request contains information about the MMS message
(e.g. size, recipient address, image coding type). The Diameter
credit-control server checks the end user's account balance, rates
the service and debits the service from the end user's account. The
granted quota is returned to the MMS Server in the Diameter Credit-
Control-Answer (3). The MMS Server acknowledges the successful
reception of the MMS message (4). The MMS Server notifies the
recipient about the new MMS (5), and the end user B retrieves the
message from the MMS message store (6),(7).
A.4 Flow IV
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MMS Server
Content Server (CC Client) B CC Server
|(1) Send MMS | | |
|--------------->| | |
| |(2) CCR (event, BALANCE_CHECK, |
| | MMS specific AVP) |
| |-------------------------------->|
| |(3) CCA (ENOUGH_CREDIT) |
| |<--------------------------------|
|(4) Send MMS Ack| | |
|<---------------| | |
| |(5) Notify MMS | |
| |--------------->| |
: : : :
| |(6) Retrieve MMS| |
| |<---------------| |
| |(7) CCR (event, DIRECT_DEBITING,|
| | MMS specific AVP) |
| |-------------------------------->|
| |(8) CCA (granted_Units) |
| |<--------------------------------|
| |(9) Retrieve MMS| |
| | Ack | |
| |--------------->| |
| | | |
Figure A.4: Flow IV
A credit control flow for Multimedia Messaging Service is shown in
Figure A.4. The recipient is charged at the message delivery.
A Content Server sends a Multimedia Message (MMS) to the MMS Server
(1) that stores the message. The message recipient will be charged
for the MMS message in this case. Since there can be substantially
long time between the reception of the message at the MMS Server and
the actual retrieval of the message, the MMS Server does not
establish any credit control session to the Diameter Credit-Control
Server but performs first only a balance check (without any credit
reservation) by sending a Diameter Credit-Control-Request
(EVENT_REQUEST with Requested-Action: BALANCE_CHECK) to verify that
the end user B's can cover the cost for the MMS (2). The Diameter
credit-control server checks the end user's account balance and
returns the answer to the MMS Server in the Diameter Credit-Control-
Answer (3). The MMS Server acknowledges the successful reception of
the MMS message (4). The MMS Server notifies the recipient about the
new MMS (5), and after some time the end user B retrieves the message
from the MMS message store (6). The MMS Server sends a Diameter
Credit-Control-Request (EVENT_REQUEST with Requested-Action:
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DIRECT_DEBITING) to the Diameter Credit-control server (7). The
Credit-Control-Request contains information about the MMS message
(e.g. size, recipient address, coding type). The Diameter credit-
control server checks the end user's account balance, rates the
service and debits the service from the end user's account. The
granted quota is returned to the MMS Server in the Diameter Credit-
Control-Request (8). The MMS is transferred to the end user B (9).
A.5 Flow V
SIP Controller
A (CC Client) B CC Server
|(1)INVITE(SDP) | | |
|--------------->| | |
| |(2) CCR (event, PRICE_ENQUIRY, |
| | SIP specific AVPs) |
| |-------------------------------->|
| |(3) CCA (Cost-Information) |
| |<--------------------------------|
| (4)MESSAGE(URL)| | |
|<---------------| | |
|(5)HTTP GET | | |
|--------------->| | |
|(6)HTTP POST | | |
|--------------->|(7)INVITE(SDP) | |
| |--------------->| |
| | (8)200 OK | |
| (9)200 OK |<---------------| |
|<---------------| | |
Figure A.5: Flow V
Figure A.5 is an example of Advice of Charge (AoC) service for SIP
call, the user A can be either postpaid or prepaid subscriber using
the AoC service. It is assumed that the SIP Controller also has HTTP
capabilities and delivers an interactive AoC web page with for
instance the cost information, the details of the call derived from
the SDP and a button to accept/not accept the charges (there may be
many other ways to deliver AoC information, however, this flow focus
on the use of the credit control messages). The user has been
authenticated and authorized prior to initiate the call and
subscribed to AoC service.
UA A sends an INVITE with SDP (1). The SIP controller determines the
user is subscribed to AoC service and sends a Diameter Credit-
Control-Request (EVENT_REQUEST with Requested-Action: PRICE_ENQUIRY)
to the Diameter credit control server (2). The Credit-Control-Request
contains SIP specific AVPs derived from the SIP signaling describing
the requested service (e.g. calling party, called party, Session
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Description Protocol attributes). The Diameter credit control server
determines the cost of the service and returns the Credit-Control-
Answer including the Cost-Information AVP (3). The SIP controller
manufactures the AoC web page with information received in SIP
signaling and with the cost information received from the credit
control server, then sends a SIP MESSAGE that contains a URL pointing
to the AoC information web page (4). At the reception of the SIP
MESSAGE the A's UA invokes automatically the web browser that
retrieves the AoC information (5). The user clicks on a proper button
and accept the charges (6). The SIP controller continues the session
and sends the INVITE to the B party that accepts the call (7,8,9).
A.6 Flow VI
Gaming Server
End-User (CC Client) CC Server
| (1)Service Delivery | |
|<---------------------->| |
: : :
: : :
| |(2)CCR(event,REFUND,Requested-
| |Service-Unit,Service-Parameter-Info)
| |----------------------->|
| | (3)CCA(Cost-Information)
| |<-----------------------|
| (4)Notification | |
|<-----------------------| |
Figure A.6: Flow VI
Figure A.6 illustrates a credit control flow for the REFUND case. It
is assumed that trusted relationship and secure connection between
the Gaming server and the Diameter credit control server exist. The
end user may be a prepaid subscriber or a postpaid subscriber.
While the end user is playing the game (1) she enters a new level
that entitles for a bonus. The Gaming server sends a Diameter Credit-
Conrol-Request (EVENT_REQUEST with Requested-Action: REFUND) to the
Diameter credit control server (2). The Credit-Control-Request
contains the Requested-Service-Unit AVP with Unit-Type set to
CREDIT_TYPE_SERVICE_SPECIFIC with the CC-Service-Specific-Units
containing the number of points the user just won. The Service-
Parameter-Info AVP is also included in the request and specifies the
service event to be rated (e.g. Tetris Bonus). The Diameter credit
control server, based on received information, determines the amount
to be credited, refunds the user's account and returns the Credit-
Control-Answer including the Cost-Information AVP (3). The Cost-
Information indicates the credited amount. At the first opportunity
the Gaming server notify the end user of the credited amount (4).
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A.7 Flow VII
SIP Controller Top-UP
A (CC Client) Server B CC Server
| | | | |
| | (1) CCR(Update,Used-Unit) | |
| |------------------------------------------>|
| | (2) CCA(Final-Unit, Redirect)|
| |<------------------------------------------|
: : : : :
: : : : :
| | (3) CCR(Update, Used-Units)| |
| |------------------------------------------>|
| | (3a)INVITE("hold") | |
| |--------------------------->| |
| | | (4) CCA(Validity-Time)|
| |<------------------------------------------|
| (5)INVITE | (6)INVITE | | |
|<--------------|------------->| | |
| (7)RTP | | |
|..............................| | |
| | (8)BYE | | |
| |<-------------| | |
| | (9)CCR(Update) | |
| |------------------------------------------>|
| | (10)CCA(Granted-Unit) |
| |<------------------------------------------|
| (12)INVITE | (11)INVITE | |
|<--------------|--------------------------->| |
Figure A.7: Flow VII
Figure A.7 is an example of the graceful service termination for a
SIP call. It is assumed the call is set up so that the controller is
in the call as a B2BUA (Back to Back User Agent). Note that the SIP
signaling is inaccurate since the focus of this flow is in the
graceful service termination and credit control authorization.
The call is ongoing between user A and user B, user A is a prepaid
user. At the expiry of the allocated quota, the SIP controller sends
a Diameter Credit-Control-Request (UPDATE_REQUEST) to the Diameter
credit control server (1). This message contains the units used this
far. The Diameter credit control server debits the used units from
the end user's account and allocates the final quota that is returned
to the SIP controller in the Diameter Credit-Control-Answer (2). This
message contains the Final-Unit-Indication AVP with: the Final-Unit-
Action set to REDIRECT, the Redirect-Address-Type set to SIP URI and
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the Redirect-Server-Address set to the Top-up server name (e.g.
sip:sip-topup-server@domain.com). At the expiry of the final
allocated quota, the SIP controller sends a Diameter Credit-Control-
Request (UPDATE_REQUEST) to the Diameter credit control server (3)
and places the called party on "hold" by sending an INVITE with the
appropriate connection address in the SDP (3a). The Credit-Control-
Request message contains the units used this far. The Diameter credit
control server debits the used units from the end user's account but
does not make any credit reservation. The Credit-Control-Answer
message, that contains the Validity-Time to supervise the graceful
service termination, is returned to the SIP controller (4). The SIP
controller establishes a SIP session between the prepaid user and the
Top-up server (5, 6). The Top-up server plays an announcement and
prompts the user to enter a credit card number and the amount of
money to be used to replenish the account (7). The Top-up server
validates the credit card number and replenishes the user's account
(using some means outside the scope of this specification) and
releases the SIP session (8). The SIP controller can now assume that
communication between the prepaid user and the Top-up server took
place and thus sends a spontaneous Credit-Control-Request
(UPDATE_REQUEST) to the Diameter credit control server to check if
the account has been replenished (9). The Diameter credit control
server reserves credit from the end user's account and return the
reserved quota to the SIP controller in the Credit-Control-Answer
(10). At this point, the SIP controller re-connects the caller and
the called party (11,12).
A.8 Flow VIII
End-User NAS AAA Server Top-up CC Server
(CC Client) Server
|(1)User Logon |(2)AA Request (CC AVPs) | |
|------------------>|------------------->| | |
| | |(3)CCR(initial, CC AVPs)
| | |------------------->|
| | |(4)CCA(Final-Unit, |
| | | Validity-Time)|
| | |<-------------------|
| |(5)AA Answer(Final-Unit,Validity-Time) |
|(6)Limited Access |<-------------------| | |
| granted | | | |
|<----------------->| | | |
| | | | |
| (7)TCP/HTTP | (8)TCP/HTTP | |
|<----------------->|<----------------------------->| |
| (9) Replenish account | |
|<------------------------------------------------->| |
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| | | (10)RAR |
| |<-------------------|<-------------------|
| | (11) RAA | |
| |------------------->|------------------->|
| |(12)CCR(update) | |
| |------------------->|(13)CCR(Update) |
| | |------------------->|
| | |(14)CCA(granted Units)
| |(15)CCA(granted Units)<------------------|
| |<-------------------| |
Figure A.8: Flow VIII
Figure A.8 is an example of the graceful service termination
initiated when the first interrogation take place due to user's
account is empty. In this example the credit control server supports
the server initiated credit re-authorization. The Diameter [NASREQ]
is implemented in the Network Access Server (NAS).
The user logs onto the network (1). The Diameter NAS first sends a
Diameter Authorization-Authentication-Request to the home Diameter
AAA Server, the credit-control client populates the AAR with the
Credit-Control AVP set to CREDIT_AUTHORIZATION and service specific
AVPs are included as usual [NASREQ]. The home Diameter AAA server
performs service specific Authentication and Authorization as usual.
The home Diameter AAA server determines that the user is a prepaid
user and notices from the Credit-Control AVP that the NAS has credit
control capabilities, it sends a Diameter Credit-Control-Request with
CC-Request-Type set to INITIAL_REQUEST to the Diameter credit-control
server to perform credit authorization (3) and to establish a credit
control session (the home Diameter AAA server may forward service
specific AVPs as received from the NAS as input for the rating
process). The Diameter credit-control server checks the end user's
account balance, determines that the account cannot cover the cost of
the sevice and initiates the graceful service termination. The
Credit-Control-Answer is returned to the home Diameter AAA server
(4). This message contains the Final-Unit-Indication AVP and the
Validity-Time AVP set to a reasonable time to give chance to the user
to replenish his/her account (e.g. 10 minutes). The Final-Unit-
Indication AVP includes: the Final-Unit-Actioin set to REDIRECT, the
Redirect-Address-Type set to ULR and the Redirect-Server-Address set
to the HTTP Top-up server name. The home Diameter AAA server sends
the received credit control AVPs to the NAS in the Diameter
Authorization-Authentication-Answer (5). Upon successful AAA the NAS
starts the credit-control session and starts immediately the graceful
service termination as instructed by the server. The NAS grant
limited access to the user (6). The HTTP client software running in
the user's device opens the transport connection that is redirected
by the NAS to the Top-up server (7,8). The user is displayed an
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appropriate web page where to enter the credit card number, the
amount of money to be used to replenish the account and with a
notification message that she will be granted unlimited access if the
replenishment operation will be successfully executed within the next
e.g. 10 minutes. The Top-up server validates the credit card number
and replenishes the user's account (using some means outside the
scope of this specification)(9). After successful account top-up the
credit control server sends a Re-Auth-Request message to the NAS
(10). The NAS acknowledges the request by returning the Re-Auth-
Answer message (11) and initiates the credit re-authorization by
sending a Credit-Control-request (UPDATE_REQUEST) to the Diameter
credit control server (12,13).
The Diameter credit control server reserves credit from the end
user's account and return the reserved quota to the NAS via the home
Diameter AAA server in the Credit-Control-Answer (14,15). The NAS
removes the restriction placed by the graceful service termination
and starts monitoring the granted units.
A.9 Flow IX
The Diameter Credit Control Application defines the Multiple-
Services-Credit-Control AVP that can be used to support independent
credit control of multiple services in a single credit control (sub-
)session for service elements that have such capabilities.
It is possible to request and allocate resources as a credit
pool that is shared between services or rating groups.
The flow example hereafter illustrates a usage scenario where the
Credit-control client and server support independent credit control
of multiple services as defined in section 5.1.1. It is assumed that
Service-Identifiers, Rating-Groups and their associated parameters
(e.g. IP 5-tuple) are locally configured in the Service Element or
provisioned by another entity than the credit control server.
End-User Service Element CC Server
(CC client)
|(1)User logon | |
|------------------>|(2)CCR(initial, Service-Id access, |
| | Access specific AVPs, |
| | Multiple-Service-Indicator) |
| |---------------------------------------->|
| |(3)CCA(Multiple-Services-CC ( |
| | Granted-Units(Total-Octets), |
| | Service-Id access, |
| | Validity-time, |
| | G-S-U-Pool-Reference(Pool-Id 1, |
| | Multiplier 10))) |
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Diameter Credit Control Application May 14, 2004
| |<----------------------------------------|
: : :
|(4)Service-Request (Service 1) |
|------------------>|(5)CCR(update, Multiple-Services-CC( |
| | Requested-Units(), Service-Id 1, |
| | Rating-Group 1)) |
| |---------------------------------------->|
| |(6)CCA(Multiple-Services-CC ( |
| | Granted-Units(Time), |
| | Rating-Group 1, |
| | G-S-U-Pool-Reference(Pool-Id 1, |
| | Multiplier 1))) |
| |<----------------------------------------|
: : :
|(7)Service-Request (Service 2) |
|------------------>| |
: : :
: : :
|(8)Service-Request (Service 3&4) |
|------------------>|(9)CCR(update, Multiple-Services-CC ( |
| | Requested-Units(), Service-Id 3, |
| | Rating-group 2), |
| | Multiple-Services-CC ( |
| | Requested-Units(), Service-Id 4, |
| | Rating-Group 3)) |
| |---------------------------------------->|
| |(10)CCA(Multiple-Services-CC ( |
| | Granted-Units(Total-Octets), |
| | Service-Id 3, Rating-group 2, |
| | Validity-time, |
| | G-S-U-Pool-Reference(Pool-Id 2, |
| | Multiplier 2)), |
| | Multiple-Services-CC ( |
| | Granted-Units(Total-Octets), |
| | Service-Id 4, Rating-group 3 |
| | Validity-time, |
| | Final-Unit-Ind.(Terminate), |
| | G-S-U-Pool-Reference(Pool-Id 2, |
| | Multiplier 5))) |
| |<----------------------------------------|
: : :
: : :
| +--------------+ | |
| |Validity time | |(11)CCR(update, |
| |expires for | | Multiple-Services-CC ( |
| |Service-Id | | Requested-Unit(), |
| | access | | Used-Units(In-Octets,Out-Octets),|
| +--------------+ | Service-Id access)) |
| |---------------------------------------->|
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Diameter Credit Control Application May 14, 2004
| |(12)CCA(Multiple-Services-CC ( |
| | Granted-Units(Total-Octets), |
| | Service-Id access, |
| | Validity-time, |
| | G-S-U-Pool-Reference(Pool-Id 1, |
| | Multiplier 10))) |
| |<----------------------------------------|
: : :
: : :
| +--------------+ | |
| |Total Quota | |(13)CCR(update, |
| |elapses for | | Multiple-Services-CC ( |
| |pool 2: | | Requested-Unit(), |
| |service 4 not | | Used-Units(In-Octets,Out-Octets),|
| |allowed, | | Service-Id 3, Rating-group 2), |
| |service 3 cont| | Multiple-Services-CC ( |
| +--------------+ | Used-Units(In-Octets,Out-Octets),|
| | Service-Id 4, Rating-group 3)) |
| |---------------------------------------->|
| |(14)CCA(Multiple-Services-CC ( |
| | Result-Code 4011, |
| | Service-Id 3)) |
| |<----------------------------------------|
: : :
: : :
|(15) User logoff | |
|------------------>|(16)CCR(term, |
| | Multiple-Services-CC ( |
| | Used-Units(In-Octets,Out-Octets),|
| | Service-Id access), |
| | Multiple-Services-CC ( |
| | Used-Units(Time), |
| | Service-Id 1, Rating-group 1), |
| | Multiple-Services-CC ( |
| | Used-Units(Time), |
| | Service-Id 2, Rating-group 1)) |
| |---------------------------------------->|
| |(17)CCA(term) |
| |<----------------------------------------|
Figure A.9: Independent credit control of multiple services in a
Credit Control (sub-)Session, flow example.
The user logs onto the network (1). The Service Element sends a
Diameter Credit-Control-Request with CC-Request-Type set to
INITIAL_REQUEST to the Diameter credit-control server to perform
credit authorization for the bearer service (e.g. internet access
service) and to establish a credit control session (2). In this
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Diameter Credit Control Application May 14, 2004
message the credit-control client indicates support for independent
credit control of multiple services within the session by including
the Multiple-Service-Indicator AVP. The Diameter credit-control
server checks the end user's account balance, based on the rating
information received from the client (i.e. Service-Id and access
specific AVPs) rates the request and reserves credit from the end
user's account. Say the server reserves $5 and determines the cost is
$1/MB. It then returns to the service element a Credit-Control-Answer
message that include the Multiple-Services-Credit-Control AVP with a
quota of 5MB associated to the Service-Id (access), to a multiplier
value of 10 and to the Pool-Id 1 (3).
The user uses Service 1 (4). The service element sends a Diameter
Credit-Control-Request with CC-Request-Type set to UPDATE_REQUEST to
the credit control server to perform credit authorization for service
1 (5). This message includes the Multiple-Services-Credit-Control AVP
to request service units for the Service 1 that belong to Rating-
Group 1. The Diameter credit-control server determines that Service 1
draws credit resources from the same account as the access service
(i.e. pool 1), based on Service-Id/Rating-Group rates the request and
updates the existing reservation by requesting more credit. Say the
server reserves $5 more (now the reservation is $10) and determines
the cost is $0.1/minutes. The server authorizes the whole Rating-
Group, it then returns to the service element a Credit-Control-Answer
message that include the Multiple-Services-Credit-Control AVP with a
quota of 50min. associated to the Rating-Group 1, to a multiplier
value of 1 and to the Pool-Id 1 (6). The client adjusts the total
amount of resources for pool 1 according the received quota, which
gives M for Pool 1 = 100.
The user uses Service 2 that belongs to the authorized Rating-Group 1
(7). Resources are then consumed from the pool 1.
The user requests now Service 3 and Service 4 as well, that are not
authorized (8). The service element sends a Diameter Credit-Control-
Request with CC-Request-Type set to UPDATE_REQUEST to the credit
control server to perform credit authorization for service 3 and 4
(9). This message includes two instances of the Multiple-Services-
Credit-Control AVP to request service units for the Service 3 that
belong to Rating-Group 2 and for the Service 4 that belong to Rating-
Group 3. The Diameter credit-control server determines that Service 3
and 4 draw credit resources from another account (i.e. pool 2), it
checks the end user's account balance and based on Service-
Ids/Rating-Groups information rates the request and reserve credit
from pool 2.
For example, the server reserves $5 and determines that Service 3
costs $0.2/MB and Service 4 costs $0.5/MB. The server authorizes only
Services 3 and 4, it then returns to the service element a Credit-
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Diameter Credit Control Application May 14, 2004
Control-Answer message that include two instances of the Multiple-
Services-Credit-Control AVP (10). One instance grants a quota of
12.5MB associated to the Service-Id 3, to a multiplier value of 2 and
to the Pool-Id 2. The other instance grants a quota of 5 MB
associated to the Service-Id 4, to a multiplier value of 5 and to the
Pool-Id 2.
The server also determines that pool 2 is exhausted and Service 4 is
not allowed to continue after these units will be consumed. Therefore
the Final-Unit-Indication AVP with action TERMINATE is associated to
the Service-Id 4. The client calculates the total amount of resources
that can be used for Pool 2 according the received quotas and
multipliers, which give M for Pool 2 = 50.
The Validity-Time for the access service expires. The service element
sends a Credit-Control-Request message to the server to perform
credit re-authorization for Service-Id (access) (11). This message
carries one instance of the Multiple-Services-Credit-Control AVP that
includes the units used by this service. Say the total amount of used
units is 4MB. The client adjusts the total amount of resources for
Pool 1 accordingly, which gives M for Pool 1 = 60.
The server deducts $4 from the user's account and updates the
reservation by requesting more credit. Say the server reserves $5
more (now the reservation is $11) and already knows the cost of the
Service-Id (access) that is $1/MB. It then returns to the service
element a Credit-Control-Answer message that include the Multiple-
Services-Credit-Control AVP with a quota of 5 MB associated to the
Service-Id (access), to a multiplier value of 10 and to the Pool-Id 1
(12). The client adjusts the total amount of resources for pool 1
according the received quota, which gives M for Pool 1 = 110.
Services 3 and 4 consume the total amount of Pool 2 credit resources
(i.e. C1*2 + C2*5 >= M). The service element immediately starts the
TERMINATE action concerning Service 4 and sends a Credit-Control-
Request message with CC-Request-Type set to UPDATE_REQUEST to the
credit control server to perform credit re-authorization for Service
3 (13). This message contains two instances of the Multiple-Services-
Credit-Control AVP to report the units used by Service 3 and Service
4. The server deducts the last $5 from the user's account (Pool 2)
and returns the answer with Result-Code 4011 in the Multiple-
Services-Credit-Control AVP to indicate that Service 3 can continue
without credit control (14).
The end user logs off from the network (15). To debit the used units
from the end user's account and to stop the credit control session,
the service element sends a Diameter Credit-Control-Request with CC-
Request-Type set to TERMINATION_REQUEST to the credit control server
(16). This message contains the units consumed by each of the used
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Diameter Credit Control Application May 14, 2004
services in multiple instances of the Multiple-Services-Credit-
Control AVP. The used units are associated with the relevant Service-
Identifier and Rating-Group. The Diameter credit-control server
debits the used units to the user's account (Pool 1) and acknowledges
the session termination by sending a Diameter Credit-Control-Answer
to the service element (17).
Author's Address
Harri Hakala
Oy L M Ericsson Ab
Joukahaisenkatu 1
20520 Turku
Finland
Phone: +358 2 265 3722
EMail: Harri.Hakala@ericsson.com
Leena Mattila
Oy L M Ericsson Ab
Joukahaisenkatu 1
20520 Turku
Finland
Phone: +358 2 265 3731
EMail: Leena.Mattila@ericsson.com
Juha-Pekka Koskinen
Nokia Networks
Hatanpaanvaltatie 30
33100 Tampere
Finland
Phone: +358 7180 74027
Email: juha-pekka.koskinen@nokia.com
Marco Stura
Nokia Networks
Hiomotie 32
00380 Helsinki
Finland
Phone: +358 7180 64308
Email: marco.stura@nokia.com
John Loughney
Nokia Research Center
Itamerenkatu 11-13
00180 Helsinki
Finland
Phone: +358 50 483 642
Email: John.Loughney@nokia.com
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Diameter Credit Control Application May 14, 2004
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