AAA Working Group
Internet Draft Harri Hakala
Document: draft-ietf-aaa-diameter-cc-00.txt Leena Mattila
Expires: December 2003 Ericsson
Juha-Pekka Koskinen
Marco Stura
John Loughney
Nokia
Diameter Credit-control Application
Status of this memo
This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026.
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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, SIP services, messaging services, download
services etc.
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1. Introduction...................................................4
1.1 Requirements language......................................4
1.2 Terminology................................................4
1.3 Advertising application support............................6
2. Architecture Models............................................7
3. Credit-Control Messages.......................................10
3.1 Credit-Control-Request (CCR) Command......................10
3.2 Credit-Control-Answer (CCA) Command.......................11
4. Credit Authorization..........................................12
4.1 First Interogation after Authorization and Authentication.14
4.2 Authorization Messages for First Interrogation............16
4.3 Session Based Credit-control..............................20
4.4 One Time Event............................................24
4.5 Credit-control Session State Machine......................29
5. Credit Control AVPs...........................................38
5.1 Abnormal-Termination-Reason AVP...........................39
5.2 CC-Correlation-Id AVP.....................................40
5.3 CC-Request-Number AVP.....................................40
5.4 CC-Request-Type AVP.......................................40
5.5 CC-Session-Failover AVP...................................41
5.6 CC-Sub-Session-Id AVP.....................................41
5.7 Check-Balance-Result AVP..................................42
5.8 Cost-Information AVP......................................42
5.9 Credit-Control AVP........................................43
5.10 Credit-Control-Failure-Handling AVP......................43
5.11 Currency-Code AVP........................................44
5.12 Direct-Debiting-Failure-Handling AVP.....................44
5.13 Exponent AVP.............................................45
5.14 Final-Unit-Indication AVP................................45
5.15 Granted-Service-Unit AVP.................................45
5.16 Requested-Action AVP.....................................46
5.17 Requested-Service-Unit AVP...............................46
5.18 Service-Parameter-Info AVP...............................47
5.19 Service-Parameter-Type AVP...............................48
5.20 Service-Parameter-Value AVP..............................48
5.21 Subscription-Id AVP......................................48
5.22 Subscription-Id-Data AVP.................................48
5.23 Subscription-Id-Type AVP.................................48
5.24 Unit-Type AVP............................................49
5.25 Unit-Value AVP...........................................49
5.26 Used-Service-Unit AVP....................................50
5.27 Value-Digits AVP.........................................50
5.28 Validity-Time AVP........................................51
6. Result Code AVP values........................................51
6.1 Transient Failure.........................................51
6.2 Permanent Failures........................................51
7. AVP Occurrence Table..........................................52
7.1 Credit Control AVP Table..................................52
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8. RADIUS/Diameter Credit-control Inter-working..................53
8.1 Initial RADIUS Access-Request.............................54
8.2 Subsequent RADIUS Access-Request message..................55
8.3 RADIUS Vendor Specific Attributes for Credit Control......56
9. IANA Considerations...........................................56
9.1 Application Identifier....................................57
9.2 Command Codes.............................................57
9.3 AVP Codes.................................................57
9.4 Result-Code AVP Values....................................57
9.5 Abnormal-Termination-Reason AVP...........................57
9.6 CC-Session-Failover AVP...................................57
9.7 Check-Balance-Result AVP..................................57
9.8 Credit-Control-Failure-Handling AVP.......................57
9.9 Direct-Debiting-Failure-Handling AVP......................58
9.10 Requested-Action AVP.....................................58
9.11 Subscription-Id-Type AVP.................................58
9.12 Unit-Type AVP............................................58
10. Credit-control Application Related Parameters................58
11. Security Considerations......................................59
12. References...................................................59
12.1 Normative................................................59
12.2 Non-Normative............................................60
13. Acknowledgement..............................................60
14. Author's Address.............................................60
15. Full Copyright Statement.....................................61
16. Notices......................................................62
17. Expiration Date..............................................62
Appendix A Credit Control sequences..............................62
A.1 Flow I....................................................62
A.2 Flow II...................................................65
A.3 Flow III..................................................66
A.4 Flow IV...................................................68
A.5 Flow V....................................................69
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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, SIP services, messaging services, download
services etc. The purpose is to provide a general solution to the
real-time cost and credit control.
The prepaid model 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 accounting
protocol. For example, the 3GPP Charging and Billing requirements
[3GPPCHARG] state that an accounting application must be able to rate
accounting information (such as service events) 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 deduct from a user account.
To fulfill these requirements, it is necessary to facilitate
communication between the network element providing the service (e.g.
NAS, SIP Proxy, Application Server etc.) and a credit-control server,
in order to minimize financial risk.
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].
1.2 Terminology
AAA
Authentication, Authorization and Accounting
AA answer
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AA answer does generically refer to a service specific authorization
and authentication answer. AA answer commands are defined in service
specific authorization applications e.g. [NASREQ] and [DiamMip].
Accounting
The act of collection of information on resource usage for the
purposes of trend analysis, auditing, billing or cost allocation.
Accounting Server
The accounting server receives accounting data from the service
elements and other devices and translates it into session records.
The processed accounting data is then submitted to a billing server,
which typically handles rating and invoice generation.
AA request
AA request does generically refer 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 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
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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.
One-time event
Basically a request/answer transaction of type event. The credit-
control server is not required to maintain session state for one-time
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 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
Credit-control process that makes use of several interrogations: the
first, possible intermediates and the final interrogation. The first
interrogation is used to reserve money from the userÆs 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
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Diameter nodes conforming to this specification MUST advertise
support by including the value of TBD (X) in the Auth-Application-Id
of the Capabilities-Exchange-Request and Capabilities-Exchange-Answer
command [DIAMBASE].
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. 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. At least two different
reasons exist to authorize a subscriber for the use of network
resources: service specific authorization and credit authorization
for prepaid users. The authentication and authorization is largely
service specific that is why different Diameter applications have
been required. Currently existing authorization applications
are[NASREQ] and [DiamMIP], other authorization applications will be
defined in the future. All the existing Diameter authorization
applications define new command codes; future Diameter authorization
applications will presumably define new command codes too.
The credit authorization is more generic and applicable to all the
service environments required to support prepaid services, therefore
the credit authorization approach shall be generic and cannot be
required to support all the current and future authorization
commands. The scope of this specification is the credit
authorization, service specific authorization and authentication is
out of the scope.
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 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 included before the service is provided to the end user.
This process is performed in order to determine potential charges and
to verify whether the end userÆs account balance is sufficient to
cover the cost of the service being rendered.
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In servive environments such as the Network Access Server (NAS) and
Mobile IP, it is a requirement 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 send 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 as
well as intermediate and final interrogations is executed with credit
control commands defined in this specification. Implementations of
credit-control client operating in 3GPP environment SHOULD support
this method. In 3GPP environment the service element sends the
request message directly to the credit-control server.
In case an implementation of the credit-control client supports both
the methods, it SHOULD be configurable what method to use.
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.
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Service Element AAA and credit-control
+----------+ +---------+ 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
Other entities, such as RADIUS AAA server, may act as a Diameter
credit-control client towards the Diameter credit-control server for
service elements that use credit control mechanisms other than
Diameter credit control. In this case the AAA server contact the
Diameter credit-control server as part of the authorization process.
The interworking architecture is illustrated in Figure 2, the
interaction between the Diameter credit-control client and the
service element is outside the scope of this specification.
Interworking with RADIUS is addressed in section 8 and Annex A.
AAA
+--------+ +---------+ protocol +------------+ +--------+
| End |<----->| Service |<------------>| AAA | |Business|
| User | | Element | | Server | |Support |
+--------+ +-->| | |+----------+|-->|System |
| +---------+ ||CC client || | |
| |+----------+| | |
+--------+ | +------^-----+ +--------+
| End |<--+ credit-control | ^
| User | protocol | |
+--------+ +-------V------+ |
|Credit-control|--------+
| Server |
+--------------+
Figure 2: Credit-control architecture with Service Element not
supporting the credit-control protocol
The credit-control server, depending on the possible service event
information, MAY perform the rating and pricing of the service event,
credit check and credit-reservation. The credit-control server, based
on the received parameters, calculates the quota granted to the end
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user for the service request. The credit-control client monitors the
consumption of the granted quota according to the instructions
returned by the credit-control server. After the service completion
the credit-control server deducts the used credit from the account.
If direct debiting/refunding is requested, the credit-control server
deducts/increases the end user's account, respectively. The credit-
control client can also enquire the price of the service or the
account balance status from the credit-control server.
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
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 units are granted to the services.
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 locate in a centralized
database. 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 and redirect
agents between credit-control client and credit-control server. These
agents transparently support the Diameter credit-control application.
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:
Command-Name Abbrev. Code Reference
-----------------------------------------------------------
Credit-Control-Request CCR TBD 3.1
Credit-Control-Answer CCA TBD 3.2
3.1 Credit-Control-Request (CCR) Command
The Credit-Control-Request message (CCR), indicated by the command-
code field set to TBD and the 'R' bit set in the Command Flags field,
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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 TBD indicating the
Diameter credit-control application.
Message Format
<Credit-Control-Request> ::= < Diameter Header: TBD, 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 ]
[ Abnormal-Termination-Reason ]
*[ Requested-Service Unit ]
*[ Service-Parameter-Info ]
*[ CC-Correlation-Id ]
*[ Proxy-Info ]
*[ Route-Record ]
*[ AVP ]
3.2 Credit-Control-Answer (CCA) Command
The Credit-Control-Answer message (CCA), indicated by the command-
code field set to TBD and the 'R' bit cleared in the Command Flags
field, is used between the credit-control server and the Diameter
AAA server to acknowledge a Credit-Control-Request command.
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Message Format
<Credit-Control-Answer> ::= < Diameter Header: TBD, REQ, 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 ]
[ Cost-Information]
[ Final-Unit-Indication ]
[ Check-Balance-Result ]
[ Credit-Control-Failure-Handling ]
[ Direct-Debiting-Failure-Handling ]
[ Validity-Time]
*[ Proxy-Info ]
*[ AVP ]
4. Credit Authorization
When an end user requests services such as for instance 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, through an AAA infrastructure, authenticates
and authorizes the user with the userÆs home network.
In case the first interrogation is not performed as part of the
authentication and authorization process the end user SHOULD be
authenticated and authorized before any request is sent to the
credit-control server. The authentication and authorization
mechanisms are outside of the scope of this document.
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.
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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 the 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.
Different Diameter authorization applications, such as [NASREQ] and
[DiamMIP] and the future Diameter authentication and authorization
applications, have been defined to meet the requirements of different
service environments. The authentication and authorization messages
in these service environments are largely application-specific, as
stated in the Diameter base [DIAMBASE] and therefore these messages
are defined in a Diameter application documents. The target of the
credit-control application defined in this document is to be a
generic credit-control application for various service scenarios that
requires credit-control capabilities. This goal is not achievable by
defining a generic authentication, authorization and credit control
message, since authentication and authorization methods are
application specific. It is not either feasible to require the
credit-control server to support all the possible authorization
commands and mandatory AVPs defined in current and future
authorization applications. Therefore this document defines two new
commands for credit authorization and mechanisms suitable to
different service environments and architectures.
The AAA infrastructure is not always implemented as discussed in
section 2, for instance in 3GPP environment the
authorization/authentication, the accounting and the credit control
servers are different physical entities that in most cases do not
communicate each others. Additionally, there might be different
requirements depending on the environment in which the credit control
application operates as discussed in section 2. Two different
approaches are then defined for the session-based credit-control to
suit properly in all the possible architectures. The first approach
uses credit-control messages after userÆs authorization and
authentication took place. The second approach uses authorization
messages for the first interrogation, which is performed during the
userÆs authorization/authentication phase, and credit-control
messages for the intermediate and the final interrogations. What
method is recommended in different environments is discussed in
section 2. Additionally, other IETF standards or standards developed
by other standardization bodies may define what is the most suitable
method in their architecture.
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-
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control). In this case the credit-control server MUST maintain the
credit control session state.
4.1 First Interogation after Authorization and Authentication
In the first approach, 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 initiate the service delivery to the end user. The
accounting protocol and the credit-control protocol can be used in
parallel, the authorization server may also drive whether the
parallel accounting stream is required.
The service element may send a service specific re-authorization
message to the Diameter 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.
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, such as in 3GPP
environment. More credit-control sequence examples are given in Annex
A.
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End-User Service Element AAA Server CC Server
(CC Client)
| Registration | AA request/answer(accounting,cc or both)|
|<----------------->|<------------------>| |
| : | | |
| : | | |
| Service Request | | |
|------------------>| | |
| | CCR(Initial,Credit-ControlAVPs) |
| +|---------------------------------------->|
| CC stream|| | CCA(Granted-Units)|
| +|<----------------------------------------|
| Service Delivery | | |
|<----------------->| ACR(start,Accounting AVPs) |
| : |------------------->|+ |
| : | ACA || Accounting stream |
| |<-------------------|+ |
| : | | |
| : | | |
| | CCR(Update Used-Units) |
| |---------------------------------------->|
| | | CCA(Granted-Units)|
| |<----------------------------------------|
| : | | |
| : | | |
| End of Service | | |
|------------------>| CCA(Termination, Used-Units) |
| |---------------------------------------->|
| | | CCA |
| |<----------------------------------------|
| | ACR(stop) | |
| |------------------->| |
| | ACA | |
| |<-------------------| |
Figure 3: Protocol example with first interrogation after userÆs
authorization/authentication
The authorization server MAY include the Credit-Control- Failure-
Handling AVP and 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. 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. The
credit-control server MAY override the failure handling for credit-
control session by including the Credit-Control-Failure-Handling AVP
in the Credit-Control-Answer.
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The Diameter credit-control server may want to control the validity
time of the granted quota and/or the production of credit-control
update requests, 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,
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 10). 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.
4.2 Authorization Messages for First Interrogation
In the second approach, the Diameter credit-control client in the
service element MUST actively contribute 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
authenticate/authorize the subscriber and determine whether or not
credit-control is required.
If credit-control is not required for the subscriber the home AAA
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 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
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credit-control server will make money reservation from the userÆs
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.
The use of the Validity-Time as discussed for the first approach is
applicable to this model as well.
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 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.
The credit-control client in this model sends further credit-control
messages to the credit-control server via the home AAA server. .
Upon receiving successful authorization answer message with the
Granted-Service-Unit, 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 intermediate request MUST be set to 1.
The next time the user issues a service request to the service
element after a previous end of service, the first interrogation is
executed with the appropriate AA request according to the service
specific authorization application, as described above. The AA
request may only be used for re-authorization and not re-
authentication (i.e. if the user is still registered and re-
authentication is not required).
The service element may send a service specific re-authorization
message to the Diameter 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.
Therefore the credit-control client MUST add to the service specific
re-authorization request the Credit-Control AVP with value set to RE-
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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 Diameter AAA server. The Diameter AAA server can make use
of this credit-control messages flow to deduce that userÆs activity
is ongoing; therefore 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 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.
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 |<-------------------|
| |<-------------------| |
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Figure 4: Protocol example with use of the
authorization messages for the first interrogation.
The following paragraphs apply to both the approaches.
The service specific re-authorization may fails during an ongoing
credit control session. In this case the user is disconnected and the
credit-control client MUST send a Credit-Control-Request message with
CC-Request-Type set to TERMINATION_REQUEST to the credit-control
server.
If the user logoff during an ongoing credit-control session or some
other reason cause 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 5 illustrates the case when the final-unit
indication causes the user logoff upon consumption of the final
granted units and STR is generated.
End-User Service Element AAA Server CC Server
(CC Client)
| Service Delivery | | |
|<----------------->| | |
| : | | |
| : | | |
| : | | |
| | | |
| | CCR(Update,Used-Units) |
| |------------------->| CCR(Update,Used-Units)
| | |------------------->|
| | | CCA(Final-Unit) |
| | CCA(Final-Unit) |<-------------------|
| |<-------------------| |
| : | | |
| : | | |
| Disconnect user | | |
|<------------------| CCR(Termination,Used-Units) |
| |------------------->| CCR(Term.,Used-Units)
| | |------------------->|
| | | CCA |
| | CCA |<-------------------|
| |<-------------------| |
| | STR | |
| |------------------->| |
| | STA | |
| |<-------------------| |
Figure 5: User disconnected due to account exhausted
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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.
A one-time event MAY be 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.
4.3 Session Based Credit-control
For a session-based credit-control, several interrogations are
needed: the first, intermediate (optional) and the final
interrogation. This is illustrated in Figure 3 and Figure 4.
4.1.1 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. In case the
first interrogation is performed as part of the
authentication/authorization process, an appropriate AA request MUST
be sent. The Subscription-Id-Data AVP SHOULD be included in the
request to identify the end-user in the credit-control server.
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 and the Service-
Parameter-Info AVP SHOULD contain the service event information to be
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rated by the credit-control server. The Service-Parameter-Info AVP
always refers to the requested service units.
The Event-Timestamp AVP contains the time when the service event is
requested in the service element.
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. However there
MUST be maximum one instance of the same unit type in one Answer
message. When the granted service units for one unit type have been
spent a new Credit-Control-Request MUST be sent to the credit-control
server even though there would be service units left for other units
types. The type of the Granted-Service-Unit AVP can be time, volume,
service specific or money depending on the type of service event. It
is not allowed to change the unit type(s) within the session.
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)
and terminate the credit-control session.
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 session. After the end user has used these
units, the Diameter credit-control client is responsible for
terminating the service session and the credit-control session by
sending the final interrogation to the credit-control server.
4.1.2 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 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
order to avoiding interruption in the service element. Even if the
granted service units reserved by the credit-control server have not
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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.
The CC-Request-Type AVP is set to the value UPDATE_REQUEST in the
intermediate request message. The Subscription-Id-Data AVP SHOULD be
included in the intermediate message to identify the end user in the
credit-control server.
The Requested-Service-Unit AVP contains the new amount of requested
service units. 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 MUST 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.
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 session. After the end user has used these
units, the Diameter credit-control client is responsible for
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terminating the service session and the credit-control session by
sending the final interrogation to the credit-control server.
There can be several intermediate interrogations within a session.
4.1.3 Final Interrogation
When the end user terminates the service session or when all the
granted units are used after a Final-Unit-Indication AVP has been
received from the credit-control server, 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.
4.1.4 Failure Procedures
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
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detected in the credit-control server based on the credit-control
server session state machine (section 4.3), Session-Id AVP and CC-
Request-Number AVP.
If a communication failure occurs during an ongoing credit-control
session the credit-control client can move the credit control message
stream to an alternative server if the value of the CC-Session-
Failover AVP is set to FAILOVER SUPPORTED. A secondary Credit control
server name received for instance from the AAA server, 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 and the credit control client will
terminate or continue the service depending on the value set in the
Credit-Control-Failure-Handling AVP. The Credit-Control-Failure-
Handling AVP MAY be sent from the authorization server and in the
Credit-Control-Answer from the credit-control server. For new credit-
control sessions, failover to an alternate credit-control server
SHOULD be performed, if possible.
The timer, Tx (as defined in section 10), is used in the credit-
control client to supervise the communication with the credit-control
server.
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 10) is used
in the credit-control server to supervise the credit-control session.
4.4 One Time Event
The one time event is used when there is no need to maintain
accounting session state in the credit-control server.
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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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.
4.2.1 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-Parameter-Info AVP in the
Credit-Control-Request message.
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 price of the requested service event is returned to the
credit-control client in the Cost-Information AVP in the Credit-
Control-Answer message.
4.2.2 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
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.
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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-Data 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 (Credit/No Credit) is returned to the
credit-control client in the Check-Balance-Result AVP in the Credit-
Control-Answer message.
4.2.3 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-Data 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 can include the monetary amount to
be charged in the Request-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, then the Service-Parameter-Info
AVP SHOULD contain the service event information to be rated by the
credit-control server. The Service-Parameter-Info AVP always refers
to the requested service unit.
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
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
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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.
4.2.4 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-Data 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 Request-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, then the Service-Parameter-Info
AVP SHOULD contain the service event information to be rated by the
credit-control server. The Service-Parameter-Info AVP always refers
to the requested service unit.
For informative purposes, the Credit-Control-Answer message MAY also
include the Cost-Information AVP containing the estimated monetary
amount of refunded unit.
4.2.5 Failure Procedure
Failover to an alternate credit-control server is allowed for one
time event since the server is not maintaining session states. There
MAY exist protocol transparent Diameter relays and redirect agents or
Diameter 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].
When the credit-control client detects a communication failure to the
credit-control server, its behavior depends on the requested action.
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The timer Tx (as defined in section 10) is used in the credit-control
client to supervise the communication with the credit-control server.
In case the requested action is Service 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 AAA server, can be used as an address of backup
server.
If the requested action is DIRECT_DEBITING and the Direct-Debiting-
Failure-Handling AVP is set to TERMINATE_OR_BUFFER the credit-control
client SHOULD terminate the service if it can determine 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. 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 can't be
delivered. If the timer Tx expires the credit-control client MUST
continue the service and eventually buffer the request according to
the value of the Direct-Debiting-Failure-Handling AVP.
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.
The implementation may choose to limit the number of re-transmission
attempts and define a re-transmission interval.
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 re-sends messages from its application level non-volatile
storage it MUST mark these request messages as possible duplicate by
setting the T-flag in the command headers as described in [DIAMBASE]
section 3.
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 server
is supporting the credit-control application the account manager
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controlling the account database MAY be responsible for duplicate
detection.
4.5 Credit-control Session 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 is to be supported are discussed in section 2 and
section 4.
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.
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 (i.e. the answer message is not received within
the validity time of the request). 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 transient failure notification in the Credit-
Control-Answer command (i.e. the peer sending back a transient
failure or temporary protocol error notification DIAMETER_TOO_BUSY,
or DIAMETER_LOOP_DETECTED in the Result-Code AVP).
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 action 'store record' means that a record is stored in the
credit-control application level non-volatile storage.
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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 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.
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
credit-control fault end user
handling equal to CONTINUE
PendingI Failure to send, or Disconnect Idle
temporary error and user/dev
credit-control fault
handling equal to TERMINATE
PendingI Tx expired and credit Disconnect Idle
Control fault handling user/dev
equal to TERMINATE
PendingI Tx expired and credit-control Grant
fault handling equal to service to Idle
CONTINUE end user
PendingI CC initial answer Disconnect Idle
received with result code user/dev
SERVICE_ DENIED or
USER_NOT_FOUND
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 and credit-control Service to
fault handling end user
equal to CONTINUE
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PendingI Failed CC initial answer Disconnect Idle
received and credit-control user/dev
failure handling equal to
TERMINATE
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 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 Disconnect PendingT
and final unit indication send
received CC termination
req.,
start Tx.
Open Change in rating condition Send PendingU
in queue CC update
req.,
Start Tx.
Open Service terminated in queue Send PendingT
CC termination
req.,
start Tx
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.,
start Tx
PendingU Successful CC update Stop Tx Open
answer received
PendingU Failure to send, or Grant Idle
temporary error and service to
credit-control fault end user
handling equal to CONTINUE
PendingU Failure to send, or Disconnect Idle
temporary error and user/dev
credit-control fault
handling equal to TERMINATE
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PendingU Tx expired and credit-control Disconnect Idle
fault handling equal to user/dev
TERMINATE
PendingU Tx expired and credit-control Grant
fault handling equal to service to Idle
CONTINUE end user.
PendingU CC update answer Disconnect Idle
received with result code user/dev
SERVICE_DENIED
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 credit service to
control fault handling equal end user.
to CONTINUE
PendingU Failed CC update Disconnect Idle
answer received and credit user/dev
control fault handling
equal to TERMINATE
PendingU User service terminated Queue PendingU
termination
event
PendingU Change in rating Queue PendingU
condition changed
rating
condition
event
PendingT Successful CC Idle
termination answer received
PendingT Tx expired Idle
PendingT Failure to send, or temporary Idle
error or failed answer
PendingT Change in rating condition PendingT
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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 Idle
answer received
PendingE Failure to send, temporary Indicate Idle
error or failed CC event service
answer received, or error
Tx expired, requested
action GET_BALANCE or
PRICE_ENQUIRY
PendingE CC event answer Disconnect Idle
received with result code user/dev
SERVICE_ DENIED or
USER_NOT_FOUND
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
answer received, or Tx to end
expired, requested user
action DIRECT_DEBITING and
fault handling equal to
CONTINUE
PendingE Failed CC event Disconnect Idle
answer received, requested user/dev
action DIRECT_DEBITING and
fault handling equal to
TERMINATE_OR_BUFFER
PendingE Failure to send or Tx Grant Idle
expired, requested service
action DIRECT_DEBITING and to end user
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fault handling equal to and store
TERMINATE_OR_BUFFER request with
T-flag
PendingE Temporary error, requested Disconnect Idle
action DIRECT_DEBITING and user/dev
fault handling equal to
TERMINATE_OR_BUFFER
PendingE Failed CC event answer Indicate Idle
received, requested service
action REFUND error and
delete request
PendingE Failure to send or Store Idle
Tx expired, requested request
action REFUND with T-flag
PendingE Temporary error Store Idle
and requested action request
REFUND
PendingB Successful CC answer Delete Idle
received request
PendingB Failed CC answer Delete Idle
received request
PendingB Failure to send or Idle
temporary error
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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,
debit units
Idle CC event request Send Idle
received, but not CC event
successfully processed. Answer with
Result-Code
!= SUCCESS
Open CC update request Send Open
received and successfully CC 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
Open CC termination request Send Idle
received, and successfully CC termin.
processed answer,
Stop Tcc,
debit used
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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 Stop Tcc, Idle
expired release
reserved
units
5. 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 4.
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.
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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST| |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Abnormal- XXX 5.1 Enumerated | - | P | | V | Y |
Termination-Reason | | | | | |
CC- XXX 5.2 OctetString| - | P | | V | Y |
Correlation-Id | | | | | |
CC-Request-Number XXX 5.3 Unsigned32 | M | P | | V | Y |
CC-Request-Type XXX 5.4 Enumerated | M | P | | V | Y |
CC-Sub-Session-Id XXX 5.5 Unsigned64 | M | P | | V | Y |
CC-Failover-Supported 5.6 Enumerated | - | P | | V | Y |
Check-Balance- XXX 5.7 Enumerated | M | P | | V | Y |
Result | | | | | |
Cost-Information XXX 5.8 Grouped | - | P | | V | Y |
Credit-Control XXX 5.9 Enumerated | M | P | | V | Y |
Credit-Control- XXX 5.10 Enumerated | M | P | | V | Y |
Failure-Handling | | | | | |
Direct-Debiting XXX 5.12 Enumerated | M | P | | V | Y |
Failure-Handling | | | | | |
Final-Unit- XXX 5.14 Unsigned32 | M | P | | V | Y |
Indication | | | | | |
Granted-Service- XXX 5.15 Grouped | M | P | | V | Y |
Unit | | | | | |
Requested-Action XXX 5.16 Enumerated | M | P | | V | Y |
Requested-Service XXX 5.17 Grouped | M | P | | V | Y |
Unit | | | | | |
Service-Parameter XXX 5.18 Grouped | M | P | | V | Y |
Info | | | | | |
Subscription-Id XXX 5.21 Grouped | M | P | | V | Y |
Used-Service-Unit XXX 5.26 Grouped | M | P | | V | Y |
Validity-Time xxx 5.28 Unsigned32 | M | P | | V | Y |
-----------------------------------------+----+-----+----+-----+----+
5.1 Abnormal-Termination-Reason AVP
The Abnormal-Termination-Reason AVP (AVP Code TBD) is of type
Enumerated and contains information about the reason for an abnormal
service termination in a service element.
The following reasons are defined:
SERVICE_ELEMENT_TERMINATION 0
An error occurred in the service element.
CONNECTION_TO_END-USER_BROKEN 1
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The connection to the end-user is broken.
5.2 CC-Correlation-Id AVP
The CC-Correlation-Id AVP (AVP Code TBD) is type of OctetString and
contains information to correlate credit control requests generated
for different components of the service, e.g. transport and service
level.
5.3 CC-Request-Number AVP
The CC-Request-Number AVP (AVP Code TBD) 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.
5.4 CC-Request-Type AVP
The CC-Request-Type AVP (AVP Code TBD) 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
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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 for the Event request
is further detailed in the Requested-Action AVP. The
Requested-AVP MUST be included in the Credit-Control-Request
message when CC-Request-Type is set to EVENT_REQUEST.
5.5 CC-Session-Failover AVP
The CC-Session-Failover AVP 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 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.
5.6 CC-Sub-Session-Id AVP
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The CC-Sub-Session-Id AVP (AVP Code 287) 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, with the exception of a CC-Request whose CC-Request-Type is
set to TERMINATION_REQUEST. A TERMINATION_REQUEST message with no CC-
Sub-Session-Id AVP present will signal the termination of all sub-
sessions for a given Session-Id.
5.7 Check-Balance-Result AVP
The Check Balance Result AVP (AVP code TBD) is of type Enumerated and
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.
5.8 Cost-Information AVP
The Cost-Information AVP (AVP Code TBD) is of type Grouped and is
used to return the cost information of a service in the Credit-
Control-Answer command. 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.
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.
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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:
<Cost-Information>::=< AVP Header: TBD >
{ Unit-Value }
{ Currency-Code }
5.9 Credit-Control AVP
The Credit-Control AVP (AVP Code TBD) is of type Enumerated and MUST
be included in AA requests when service element has credit control
capabilities.
CREDIT_AUTHORIZATION 0
If the 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.
5.10 Credit-Control-Failure-Handling AVP
The Credit-Control-Failure-Handling AVP (AVP Code TBD) 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.
TERMINATE 0
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
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credit-control server. If the credit-control client does not receive
any Credit-Control-Answer message within the Tx timer (as defined in
section 10) the credit-control request is regarded failed. The moving
of already started credit-control session to alternative server is
not allowed.
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
service SHOULD be granted even if credit-control messages can't be
delivered.
5.11 Currency-Code AVP
The Currency-Code AVP (AVP Code TBD) 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.
5.12 Direct-Debiting-Failure-Handling AVP
The Direct-Debiting-Failure-Handling AVP (AVP Code TBD) 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 10) 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-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
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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.
5.13 Exponent AVP
Exponent AVP is of type Integer32 (AVP code TBD) and contains the
exponent value to be applied for the Value-Digit AVP within the Unit-
Value AVP.
5.14 Final-Unit-Indication AVP
The Final-Unit-Indication AVP (AVP Code TBD) is of type Unsigned32
and indicates that the Granted-Service-Unit AVP in the accounting
command contains the final units for the service. After these units
have expired, the Diameter credit-control client is responsible for
terminating the service and sending the TERMINATION_REQUEST to the
credit-control server.
If more than one unit types are received in the Credit-Control-
Answer, the Unit type which first expired SHOULD cause the
termination.
If included in a command, the value of this AVP is always 1.
5.15 Granted-Service-Unit AVP
Granted-Service-Unit AVP (AVP Code TBD) 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. The Unit-Value AVP contains
the granted units and the Unit-Type AVP defines the type of the unit.
If the Unit-Type AVP is set to time in the Credit-Control-Answer or
AA Answer command, the Unit Value AVP specifies the granted time in
seconds.
If the Unit-Type AVP is set to volume in the Credit-Control-Answer or
AA Answer command, the Unit-Value AVP specifies the granted volume in
bytes.
If the Unit-Type AVP is set to service specific in the Credit-
Control-Answer command or AA Answer, the Unit-Value AVP specifies the
granted number of service specific units (e.g. number of events,
points) given in a selected service.
If the Unit-Type AVP is set to money in the Credit-Control-Answer or
AA answer command, the Unit-Value AVP specifies the granted monetary
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amount in the given currency. If the unit type is money, a Currency-
Code AVP SHOULD be included.
It has the following ABNF grammar:
<Granted-Service-Unit>::=< AVP Header: TBD >
{ Unit-Type }
{ Unit-Value }
[ Currency-Code ]
5.16 Requested-Action AVP
The Requested-Action AVP (AVP Code TBD) 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-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-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.
5.17 Requested-Service-Unit AVP
The Requested-Service-Unit AVP (AVP Code TBD) is of type Grouped and
contains the amount of requested units specified by the Diameter
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credit-control client. The included Unit-Value AVP contains the
requested Unit-Value and the Unit-Type AVP defines the type of the
unit. A server is not required to implement all of the unit types,
and must treat unknown or unsupported unit types as invalid AVP
values.
If the Unit Type AVP is set to time in the Credit-Control-Request
command, the Unit-Value AVP specifies the requested time in seconds.
If the Unit-type AVP is set to volume in the Credit-Control-Request
command, the Unit-Value AVP specifies the requested volume in bytes.
If the Unit-type AVP is set to service specific in the Credit-
Control-Request command, the Unit-Value AVP specifies the requested
number of service specific units (e.g. number of events) given in a
selected service.
If the Unit-Type AVP is set to money in the Credit-Control-Request
command, the Unit-Value AVP specifies the monetary amount in the
given currency. If the unit type is money, a Currency-Code AVP SHOULD
be included.
It has the following ABNF grammar:
<Requested-Service-Unit>::=< AVP Header: TBD >
{ Unit-Type }
{ Unit-Value }
[ Currency-Code ]
5.18 Service-Parameter-Info AVP
The Service-Parameter-Info AVP (AVP Code TBD) 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
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:
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<Service-Parameter-Info>::=< AVP Header: TBD >
[ Service-Parameter-Type ]
[ Service-Parameter-Value ]
5.19 Service-Parameter-Type AVP
The Service-Parameter-Type AVP is of type Unsigned32 (AVP Code TBD)
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 Service-Parameter-Value AVP
contains the service parameter type.
5.20 Service-Parameter-Value AVP
The Service-Parameter-Value AVP is of type UTF8String (AVP Code TBD)
and contains the value of the service parameter type.
5.21 Subscription-Id AVP
The Subscription-Id AVP (AVP Code TBD) 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-Data }
{ Subscription-Id-Type }
5.22 Subscription-Id-Data AVP
The Subscription-Id-Data AVP (AVP Code TBD) is used to identify the
end-user and is of type UTF8String. The Subscription-Id-Type AVP
defines which type of identifier is used.
5.23 Subscription-Id-Type AVP
The Subscription-Id-Type AVP (AVP Code TBD) 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_MSISDN 0
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The identifier is in international MSISDN format, 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_URL 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.
5.24 Unit-Type AVP
The Unit-Type AVP is of type Enumerated (AVP Code TBD) and contains
the type of the unit.
The unit type can be one of the following:
CREDIT_TYPE_TIME 0
The unit is of type time, given in seconds.
CREDIT_TYPE_VOLUME 1
The unit is of type volume, given in bytes.
CREDIT_TYPE_SERVICE_SPECIFIC 2
The unit is service specific (e.g. number of events,
points, chips, services etc), given in a selected service.
CREDIT_TYPE_MONEY 3
The unit is of type money, given as a monetary value, whose
currency SHOULD be specified by the Currency-Code AVP.
5.25 Unit-Value AVP
Unit-Value AVP is of type Grouped (AVP Code TBD). The value can be
time in seconds, volume in bytes, number of service specific units or
monetary amount depending on the given unit type. 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
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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 ]
5.26 Used-Service-Unit AVP
The Used-Service-Unit AVP is of type Grouped AVP (AVP Code TBD) 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 included Unit-Type AVP defines the type of the unit and
the Unit-Value AVP contains the used amount.
If the Unit Type AVP is set to time in the Credit-Control-Request
command, the Unit-Value AVP specifies the used time in seconds.
If the Unit-Type AVP is set to volume in the Credit-Control-Request
command, the Unit-Value AVP specifies the used volume in bytes.
If the Unit-type AVP is set to service specific in the Credit-
Control-Request command, the Unit-Value AVP specifies the used number
of service specific units (e.g. number of events) given in a selected
service.
If the Unit-Type AVP is set to money in the Credit-Control-Request
command, the Unit-Value AVP specifies the used monetary amount in the
given currency. If the unit type is money, a Currency-Code AVP SHOULD
be included.
It has the following ABNF grammar:
<Used-Service-Unit>::=< AVP Header: TBD >
{ Unit-Type }
{ Unit-Value }
[ Currency-Code ]
5.27 Value-Digits AVP
The Value-Digits AVP is of type Unsigned64 (AVP code TBD) and
contains the number of seconds, volume in bytes, number of service
specific units or monetary amount depending on the given Unit-Type
AVP. 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.
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5.28 Validity-Time AVP
The Validity-Time AVP is of type Unsigned32 (AVP code TBD) and is
sent from the credit-control server to the credit-control client. The
AVP contains the validity time of the granted service units. 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 request to the server with CC-Request-Type set to
UPDATE_REQUEST. The value field of the Validity-Time AVP is given in
seconds.
6. 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.
6.1 Transient Failure
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 40XX
The credit-control server denies the service request due to
service restrictions or limitations related to the end-user,
for example the end-user's account could not cover the requested
service. The possibly reported used-service-units with the CCR
are deducted.
DIAMETER_CREDIT_CONTROL_NOT_APPLICABLE 40XX
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).
6.2 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 50XX
The specified end user is unknown in the credit-control server.
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DIAMETER_RATING_FAILED 50xx
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.
7. 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:
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.
7.1 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.
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+-----------+
| Command |
| Code |
|-----+-----+
Attribute Name | CCR | CCA |
------------------------------|-----+-----+
Abnormal-Termination-Reason | 0-1 | 0 |
Acct-Multi-Session-Id | 0-1 | 0-1 |
Auth-Application-Id | 1 | 1 |
CC-Correlation-Id | 0-1 | 0 |
CC-Failover-Supported | 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- | 0-1 | 0-1 |
Handling | | |
Destination-Host | 0-1 | 0 |
Destination-Realm | 1 | 0 |
Direct-Debiting-Failure- | 0-1 | 0-1 |
Handling AVP | | |
Event-Timestamp | 0-1 | 0-1 |
Final-Unit-Indication | 0 | 0-1 |
Granted-Service-Unit | 0 | 0+ |
Origin-Host | 1 | 1 |
Origin-Realm | 1 | 1 |
Origin-State-Id | 0-1 | 0-1 |
Proxy-Info | 0+ | 0+ |
Requested-Action | 0-1 | 0 |
Requested-Service-Unit | 0-1 | 0 |
Route-Record | 0+ | 0+ |
Service-Parameter-Info | 0+ | 0 |
Session-Id | 1 | 1 |
Subscription-Id | 0-1 | 0-1 |
Used-Service-Unit | 0+ | 0 |
User-Name | 0-1 | 0-1 |
Validity-Time | 0-1 | 0-1 |
------------------------------|-----+-----+
8. RADIUS/Diameter Credit-control Inter-working
This section defines some basic guidelines to provide the Diameter
Credit- control/RADIUS inter-working, that is a protocol translation
between RADIUS [RFC2865] and Diameter Credit-control application. A
complete description of all protocol translations between RADIUS and
Diameter Credit-control application is beyond the scope of this
document. Note that this document does not restrict implementations
from creating additional methods; it just provides some guiding
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Diameter Credit Control Application June 2003
principles for protocol translation. Translation makes use of RADIUS
Vendor Specific Attributes (VSAs) for transporting Diameter credit-
control AVPs.
The Diameter NASREQ [NASREQ] application defines how a RADIUS Request
is forwarded as a Diameter Request. Guidelines defined in the
Diameter NASREQ should be followed to the appropriate extent.
A protocol translation between RADIUS and Diameter Credit-control
application is shown in Annex A.
8.1 Initial RADIUS Access-Request
When an AAA server acting as a Translation Agent receives an initial
RADIUS Access-Request message indicating that the service element is
capable of credit-control (e.g. Radius VSA Pre-Paid-Accounting-
Capability), and if the AAA server determines that the subscriber is
a prepaid subscriber then a Diameter Credit control request MUST be
sent towards the credit-control server.
In addition to those steps defined in [NASREQ] the AAA server should
perform the following steps related to the protocol translation
between RADIUS and Diameter Credit-control application:
- The credit control Session-Id should be included in the
Session-Id AVP.
- The CC-Request-Type is set to INITIAL_REQUEST and CC-Request-
Number value is set to 0.
- Subscription-Id should be added using User-Name attribute from
the RADIUS Access-Request message or some AAA server local Id
to identify userÆs credit control subscription.
- If the Access-Request message contains the Event-Timestamp
attribute it should be included in the Event-Timestamp AVP
The following steps are applied to response the Access-Request
message when successful credit-control answer is received from the
Credit-control server:
- The AAA server shall generate a RADIUS VSA Quota Id to
correlate subsequent RADIUS message with the credit-control
session.
- The Termination-Action attribute must be set to be æRADIUS-
requestÆ to ensure that the used quota is returned by the
service element upon termination of the service.
- If the Granted-Service-Unit AVP with the Unit-Type Time or the
Validity-Time AVP is returned by the credit control server,
then the smallest value should be included in the RADIUS VSA
Duration-Quota.
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- If the Granted-Service-Unit AVP with the Unit-Type Volume is
returned by the credit-control server, then the volume should
be included in the RADIUS VSA Volume-Quota.
- If separate RADIUS VSA Thresholds (volume or duration) are
required by RADIUS implementation, the AAA server shall derive
the threshold values from the Granted-Service-Unit AVPs. The
threshold should be less than the Duration-Quota or Volume-
Quota, except when the Final-Unit-Indication AVP is returned by
the credit control server.
When credit-control answer message includes the Result-Code, which
indicates that credit control authorization is rejected, the AAA
server shall send an Access-Reject message to service element.
8.2 Subsequent RADIUS Access-Request message
When an AAA server receives a RADIUS Access-Request message
containing RADIUS VSA Quota Id, it indicates that the Access-Request
message is subsequent RADIUS Request related to the credit control
session. The AAA server shall use the Quota Id to identify the
credit-control session.
The AAA serverÆs next steps depend on the value of the RADIUS VSA
Update-Reason. If the Update-Reason indicates æThreshold reachedÆ
then the AAA server should perform the following steps related to a
new quota request:
- The CC-Request-Type is set to UPDATE_REQUEST and CC-Request-
Number value is increased by one.
- If the RADIUS Access-Request message contains the RADIUS VSA
Volume-Quota, the value shall be included in the Used-Service-
Unit AVP and Unit-Type shall be set to Volume.
- If the RADIUS Access-Request message contains RADIUS VSA Time-
Quota, the value shall be included in the Used-Service-Unit AVP
and the Unit-Type shall be set to Time.
The reply to the RADIUS Access-Request message shall be handled as
described in initial Radius Access-Request.
If the RADIUS VSA Update-Reason indicates that the associated
resources are released at the service element, then the AAA server
shall terminate the credit control session by performing the
following steps:
- The CC-Request-Type is set to TERMINATION_REQUEST and CC-Request-
Number value is increased by one.
- If RADIUS VSA Volume-Quota, the value shall be included in the
Used-Service-Unit AVP and Unit-Type shall be set to Volume.
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Diameter Credit Control Application June 2003
- If RADIUS VSA Time-Quota, the value shall be included in the
Used-Service-Unit AVP and the Unit-Type shall be set to Time.
After the AAA server receives response to the final credit Control
Credit-Control-Request the RADIUS Access-Accept message shall be
return to the service element.
8.3 RADIUS Vendor Specific Attributes for Credit Control
To provide the credit control for RADIUS implementation the RADIUS
Vendor Specific Attributes (VSAs) are used for transporting Diameter
credit-control AVPs. The RADIUS Type 26 (= Vendor-Specific) is used
for RADIUS VSA.
RADIUS Inter-working with the Diameter Credit control uses the
following VSA included with the RADIUS Access Request and Access
Accept messages:
- Pre-Paid-Accounting-Capability; defines that the Service
element in RADIUS implementation is capable of credit-control.
- Quota Id; generated by the AAA server and it is used to
correlate subsequent RADIUS message with the credit-control
session.
- Duration-Quota; in RADIUS Access-Request message it indicates
the used Duration and in RADIUS Access-Accept message it
indicates the Duration allocated for the service element.
- Volume-Quota; in RADIUS Access-Request message it indicates the
used Volume and in RADIUS Access-Accept message it indicates
the Volume allocated for the service element.
- Volume-Threshold; If RADIUS implementation requires separate
threshold attribute for Volume, then Volume-Threshold is sent
in RADIUS Access-Accept message and it represents the volume
(in bytes) that shall be used by the service element before
requesting a new Volume quota.
- Duration-Threshold; If RADIUS implementation requires separate
threshold attribute for Duration, then Duration-Threshold is
sent in RADIUS Access-Accept message and it represents the
duration (in seconds) that shall be used by the service element
before requesting a new Duration quota.
- Update-Reason; in RADIUS Access-Request message it indicates
the reason for the initiating the quota update operation.
9. 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.
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Diameter Credit Control Application June 2003
9.1 Application Identifier
This specification assigns the value TBD to the Application
Identifier namespace defined in [DIAMBASE]. See section 1.3 for more
information.
9.2 Command Codes
This specification uses the value XXX [TBD] from the Command code
namespace defined in [DIAMBASE].
9.3 AVP Codes
This specification assigns the values TBD - TBD from the AVP code
namespace defined in [DIAMBASE] See section 4.0 for the assignment of
the namespace in this specification.
9.4 Result-Code AVP Values
This specification assigns the values 40XX and 50XX from the Result-
Code AVP (AVP Code 268) value namespace defined in [DIAMBASE]. See
section 5.0 for the assignment of the namespace in this
specification.
9.5 Abnormal-Termination-Reason AVP
As defined in Section 4.1, the Abnormal-Termination-Reason AVP (AVP
Code TBD) defines the values 0-1. All remaining values are available
for assignment via Designated Expert [IANA].
9.6 CC-Session-Failover AVP
As defined in section 5.6, the CC-Failover-Supported AVP (AVP code
TBD) defines the value 0-1. All remaining values are available for
assignment via Designated Expert [IANA].
9.7 Check-Balance-Result AVP
As defined in Section 4.3, the Check-Balance-Result AVP (AVP Code
TBD) defines the values 0-1. All remaining values are available for
assignment via Designated Expert [IANA].
9.8 Credit-Control-Failure-Handling AVP
As defined in Section 4.6, the Credit-Control-Failure-Handling AVP
(AVP Code TBD) defines the values 0-1. All remaining values are
available for assignment via Designated Expert [IANA].
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9.9 Direct-Debiting-Failure-Handling AVP
As defined in Section 4.8, the Direct-Debiting-Failure-Handling AVP
(AVP Code TBD) defines the values 0-1. All remaining values are
available for assignment via Designated Expert [IANA].
9.10 Requested-Action AVP
As defined in Section 4.11, the Requested-Action AVP (AVP Code TBD)
defines the values 0-3. All remaining values are available for
assignment via Designated Expert [IANA].
9.11 Subscription-Id-Type AVP
As defined in Section 4.17, the Subscription-Id-Type AVP (AVP Code
TBD) defines the values 0-4. All remaining values are available for
assignment via Designated Expert [IANA].
9.12 Unit-Type AVP
As defined in Section 4.20, the Unit-Type AVP (AVP Code TBD) defines
the values 0-3. All remaining values are available for assignment via
Designated Expert [IANA].
10. 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
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.
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
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Diameter Credit Control Application June 2003
Client implementations may offer the possibility to locally
configure these AVPs. In such a case their value and behavior is
defined in section 4.1.4 for the Credit-Control-Failure-Handling
and in section 4.7 for the Direct-Debiting-Failure-Handling.
The credit control server may override the failure handling by
including for credit control session by including the Credit-
Control-Failure-Handling AVP in the Credit-Control-Answer
command.
11. Security Considerations
The security models as defined in the Diameter base protocol
[DIAMBASE] applies to this application too.
12. References
12.1 Normative
[DIAMBASE] P. Calhoun, J. Arkko, E. Guttman, G. Zorn, J. Loughney
"Diameter Base Protocol", IETF work in progress.
[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
Hakala et al. Expires - December 2003 [Page 59]
Diameter Credit Control Application June 2003
1999.
[IANA] Narten, Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434,
October
1998
12.2 Non-Normative
[KEYWORDS] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[ACCMGMT] B.Aboba, J.Arkko, D.Harrington. "Introduction to
Accounting Management", RFC 2975, October 2000.
[RFC2866] C.Rigney. "Radius Accounting", RFC 2866, June 2000
[NASREQ] P. Calhoun, G. Zorn, D. Spence, D. Mitton. "Diameter
NASREQ Application", IETF work in progress.
[DIAMMIP] P. Calhoun, T. Johansson, C. Perkins "Diameter Mobile IP
Application",
IETF work in progress.
[RFC2865] C. Rigney, S. Willens, A. Rubens, W. Simpson.
"Remote Authentication Dial In User Service (RADIUS), RFC
2865, June 2000
13. Acknowledgement
The authors would like to thank Bernard Aboba, Avi Lior, Paco Marin
and our colleagues at Ericsson and Nokia for their comments and
suggestions.
14. Author's Address
Harri Hakala
Oy L M Ericsson Ab
Joukahaisenkatu 1
20520 Turku
Finland
Phone: +358 2 265 3722
EMail: Harri.Hakala@ericsson.fi
Leena Mattila
Oy L M Ericsson Ab
Joukahaisenkatu 1
20520 Turku
Finland
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Diameter Credit Control Application June 2003
Phone: +358 2 265 3731
EMail: Leena.Mattila@ericsson.fi
Juha-Pekka Koskinen
Nokia Networks
Hatanpaanvaltatie 30
33100 Tampere
Finland
Phone: +358 7180 74027
Email: juha-pekka.koskinen@nokia.com
Marco Stura
Nokia Networks
Valimotie 21
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
15. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English. The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
Hakala et al. Expires - December 2003 [Page 61]
Diameter Credit Control Application June 2003
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
16. Notices
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights, which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
17. Expiration Date
This memo is filed as <draft-ietf-aaa-diameter-cc-00.txt> and expires
in December 2003.
Appendix A Credit Control sequences
A.1 Flow I
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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) | |
| |(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.
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Diameter Credit Control Application June 2003
The user logs onto the network (1). The Diameter NAS first sends a
Diameter Authorization-Authentication-Request to the home 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 AAA server performs service
specific Authentication and Authorization as usual. The 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 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 AAA server in the Diameter
Credit-Control-Answer (4). The Home 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 Home AAA server (7). This message
contains the units used this far. The 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 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 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 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 AAA
server (14). The 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 AAA server (16). The AAA server forwards the answer to the
NAS (17). STR/STA take place between NAS and Home AAA server as
usual (18-19).
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A.2 Flow II
AAA Server
NAS (CC Client) CC Server
|(1) Access-Request | |
|----------------------->| |
| |(2) CCR (initial) |
| |----------------------->|
| |(3) CCA (granted_Units) |
| |<-----------------------|
|(4) Access-Accept | |
| (granted Units) | |
|<-----------------------| |
: : :
|(5) Access-Request | |
| (used Units) | |
|----------------------->| |
| |(6) CCR (update, |
| | used Units, |
| |----------------------->|
| |(7) CCA (granted_Units) |
| |<-----------------------|
|(8) Access-Accept | |
| (granted Units) | |
|<-----------------------| |
: : :
|(9) Access-Request | |
|----------------------->| |
| |(10) CCR (termin., |
| | used Units) |
| |----------------------->|
| |(11) CCA |
| |<-----------------------|
|(12) Access-Accept | |
|<-----------------------| |
| | |
Figure A.2: Flow II
A credit control flow for RADIUS prepaid - Diameter credit control
interworking is shown in Figure A.2. The focus of this flow is in the
AAA Server (Diameter credit-control client) and Diameter credit-
control server interworking.
The NAS first sends a RADIUS Access-Request to the home AAA Server
(1). The home AAA server performs regular Authentication and
Authorization. When the AAA server notices that the user is a prepaid
user it sends a Diameter Credit-Control-Request with CC-Request-Type
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Diameter Credit Control Application June 2003
set to INITIAL_REQUEST to the Diameter credit-control server to
perform credit authorization (2) and to establish a credit control
session. 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 (3). The Home AAA server sends
the reserved quota to the NAS in the RADIUS Access-Accept (4). At the
expiry of the allocated quota, the NAS sends a new RADIUS Access-
Request to the Home AAA server (5). This message contains the units
used this far. The units are reported to the Diameter credit-control
server in a Diameter Credit-Control-Request (UPDATE_REQUEST) (6). 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 (7). The quota is
transferred to the NAS in the RADIUS Access-Accept (8). When the end
user terminates the service the NAS sends a RADIUS Access-Request
(9). 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 (10). The Diameter credit-control server acknowledges the
session termination by sending a Diameter Credit-Control-Answer to
the Home AAA server (11). The RADIUS Access-Accept is sent to the NAS
(12).
A.3 Flow III
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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 | |
| |---------------------------->| |
: : : :
| |(5) CCR (update, used Units) |
| |------------------------------------------->|
| |(6) CCA (granted_Units) |
| |<-------------------------------------------|
: : : :
|(7) BYE | | |
|------------->| | |
| |(8) BYE | |
| |---------------------------->| |
| |(9) CCR (termination, used Units)----------|
| |------------------------------------------->|
| |(10) CCA () |
| |<-------------------------------------------|
| | | |
Figure A.3: Flow III
The end user (SIP User Agent A) sends REGISTER with credentials (i).
The SIP Proxy sends a request to the AAA server to perform Multimedia
authentication and authorization by using for instance Diameter
Multimedia application (ii). The 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
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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 userÆs account balance,
rates the service and reserves credit from the end userÆs 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). BÆs 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 userÆs 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
Credit-control server acknowledges the session termination by sending
a Diameter Credit-Control-Answer to the SIP Proxy (10).
A.4 Flow IV
MMS Server
A (CC Client) B CC Server
|(1) Send MMS | | |
|--------------->| | |
| |(2) CCR (event, DIRECT_DEBITING,|
| | MMS specific AVP) |
| |-------------------------------->|
| |(3) CCR (granted_Units) |
| |<--------------------------------|
|(4) Send MMS Ack| | |
|<---------------| | |
| |(5) Notify MMS | |
| |--------------->| |
: : : :
| |(6) Retrieve MMS| |
| |<---------------| |
| |(7) Retrieve MMS| |
| | Ack | |
| |--------------->| |
| | | |
Figure A.4: Flow IV
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A credit control flow for Multimedia Messaging Services is shown in
Figure A.4. 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 userÆs account balance, rates
the service and debits the service from the end userÆs 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.5 Flow V
MMS Server
Content Server (CC Client) B CC Server
|(1) Send MMS | | |
|--------------->| | |
| |(2) CCR (event, BALANCE_CHECK, |
| | MMS specific AVP) |
| |-------------------------------->|
| |(3) CCA (OK) |
| |<--------------------------------|
|(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.5: Flow V
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A credit control flow for Multimedia Messaging Service is shown in
Figure A.5. 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 BÆs can cover the cost for the MMS (2). The Diameter
credit-control server checks the end userÆs 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:
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 userÆs account balance, rates the
service and debits the service from the end userÆs 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).
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