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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or cite them other than as "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/lid-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html 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. Hakala et al. Expires - December 2003 [Page 1] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 2] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 3] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 4] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 5] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 6] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 7] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 8] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 9] Diameter Credit Control Application June 2003 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, Hakala et al. Expires - December 2003 [Page 10] Diameter Credit Control Application June 2003 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 ::= < 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. Hakala et al. Expires - December 2003 [Page 11] Diameter Credit Control Application June 2003 Message Format ::= < 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. Hakala et al. Expires - December 2003 [Page 12] Diameter Credit Control Application June 2003 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- Hakala et al. Expires - December 2003 [Page 13] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 14] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 15] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 16] Diameter Credit Control Application June 2003 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- Hakala et al. Expires - December 2003 [Page 17] Diameter Credit Control Application June 2003 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 |<-------------------| | |<-------------------| | Hakala et al. Expires - December 2003 [Page 18] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 19] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 20] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 21] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 22] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 23] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 24] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 25] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 26] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 27] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 28] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 29] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 30] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 31] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 32] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 33] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 34] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 35] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 36] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 37] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 38] Diameter Credit Control Application June 2003 +---------------------+ | 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 Hakala et al. Expires - December 2003 [Page 39] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 40] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 41] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 42] Diameter Credit Control Application June 2003 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: ::=< 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 Hakala et al. Expires - December 2003 [Page 43] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 44] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 45] Diameter Credit Control Application June 2003 amount in the given currency. If the unit type is money, a Currency- Code AVP SHOULD be included. It has the following ABNF grammar: ::=< 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 Hakala et al. Expires - December 2003 [Page 46] Diameter Credit Control Application June 2003 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: ::=< 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: Hakala et al. Expires - December 2003 [Page 47] Diameter Credit Control Application June 2003 ::=< 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: ::=< 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 Hakala et al. Expires - December 2003 [Page 48] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 49] Diameter Credit Control Application June 2003 Exponent = -1. The absence of exponent part MUST be interpreted as exponent being equal to zero. It has the following ABNF grammar: ::=< 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: ::=< 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. Hakala et al. Expires - December 2003 [Page 50] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 51] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 52] Diameter Credit Control Application June 2003 +-----------+ | 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 Hakala et al. Expires - December 2003 [Page 53] 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. Hakala et al. Expires - December 2003 [Page 54] Diameter Credit Control Application June 2003 - 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. Hakala et al. Expires - December 2003 [Page 55] 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. Hakala et al. Expires - December 2003 [Page 56] 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]. Hakala et al. Expires - December 2003 [Page 57] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 58] 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 Hakala et al. Expires - December 2003 [Page 60] 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 and expires in December 2003. Appendix A Credit Control sequences A.1 Flow I Hakala et al. Expires - December 2003 [Page 62] Diameter Credit Control Application June 2003 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. Hakala et al. Expires - December 2003 [Page 63] 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). Hakala et al. Expires - December 2003 [Page 64] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 65] 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 Hakala et al. Expires - December 2003 [Page 66] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 67] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 68] Diameter Credit Control Application June 2003 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 Hakala et al. Expires - December 2003 [Page 69] Diameter Credit Control Application June 2003 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). Hakala et al. Expires - December 2003 [Page 70]