RFC 8506
Diameter Credit-Control Application
7. Credit-Control Application State Machines
This section defines five credit-control application state machines. The first four state machines are to be observed by credit-control clients. The first state machine describes session-based credit-control where the first interrogation is executed as part of the authorization/ authentication process. The second state machine describes session-based credit-control where the first interrogation is executed after the authorization/authentication process. The requirements regarding what has to be supported for these two state machines are discussed in Section 5.2. The third state machine describes session-based credit-control for the intermediate and final interrogations. The fourth state machine describes event-based credit-control. These two state machines are to be observed by all implementations that conform to this specification. The fifth state machine describes the credit-control session from a credit-control server's perspective. Any event not listed in the state machines MUST be considered an error condition, and a corresponding answer, if applicable, MUST be returned to the originator of the message. In Tables 3, 4, and 5, the event "failure to send" means that the Diameter Credit-Control client is unable to communicate with the desired destination or, if a failover procedure is supported, with a possibly defined alternative destination (e.g., the request times out and the Answer message is not received). This could be due to (1) the peer being down or (2) a physical link failure in the path to or from the credit-control server. The event "temporary error" means that the Diameter Credit-Control client received a protocol error notification (DIAMETER_TOO_BUSY, DIAMETER_UNABLE_TO_DELIVER, or DIAMETER_LOOP_DETECTED) in the Result-Code AVP of the Credit-Control-Answer command. This type of notification may ultimately be received in answer to the retransmitted request to a defined alternative destination, if failover is supported.
The event "failed answer" means that the Diameter Credit-Control client received a non-transient failure (permanent failure) notification in the Credit-Control-Answer command. This type of notification may ultimately be received in answer to the retransmitted request to a defined alternative destination, if failover is supported. The action "store request" means that a request is stored in credit-control application-level non-volatile storage. The event "not successfully processed" means that the credit-control server could not process the message, e.g., due to an unknown end user, an account being empty, or errors defined in [RFC6733]. The event "user service terminated" can be triggered for various reasons, e.g., normal user termination, network failure, and ASR (Abort-Session-Request). The Termination-Cause AVP contains information about the reason for termination, as specified in [RFC6733]. The Tx timer, which is used to control the waiting time in the credit-control client in the Pending state, is stopped upon exit of the Pending state. The stopping of the Tx timer is omitted in the state machine when the new state is Idle, as moving to Idle state implies the clearing of the session and all the variables associated to it. The states PendingI, PendingU, PendingT, PendingE, and PendingB stand for pending states to wait for an answer to a credit-control request related to Initial, Update, Termination, Event, or Buffered request, respectively. In Table 2, failover to a secondary server upon "temporary error" or "failure to send" is not explicitly described. However, moving an ongoing credit-control message stream to an alternative server is possible if the CC-Session-Failover AVP is set to FAILOVER_SUPPORTED, as described in Section 5.7. Resending a credit-control event to an alternative server is supported as described in Section 6.5.
+----------+-------------------------------+-------------+----------+ | State | Event | Action | New | | | | | State | +----------+-------------------------------+-------------+----------+ | Idle | Client or device requests | Send | PendingI | | | access/service | AA-Request | | | | | with added | | | | | CC AVPs, | | | | | start Tx | | | | | timer | | | | | | | | PendingI | Successful answer to | Grant | Open | | | AA-Request received | service to | | | | | end user, | | | | | stop Tx | | | | | timer | | | | | | | | PendingI | Tx timer expired | Disconnect | Idle | | | | user/dev | | | | | | | | PendingI | Failed AA-Answer received | Disconnect | Idle | | | | user/dev | | | | | | | | PendingI | AA-Answer received with | Grant | Idle | | | Result-Code equal to | service to | | | | CREDIT_CONTROL_NOT_APPLICABLE | end user | | | | | | | | PendingI | User service terminated | Queue | PendingI | | | | termination | | | | | event | | | | | | | | PendingI | Change in rating condition | Queue | PendingI | | | | changed | | | | | rating | | | | | condition | | | | | event | | +----------+-------------------------------+-------------+----------+ Table 2: Session-Based Client State Machine for the First Interrogation with AA-Request
+----------+-------------------------------+-------------+----------+
| State | Event | Action | New |
| | | | State |
+----------+-------------------------------+-------------+----------+
| Idle | Client or device requests | Send CC | PendingI |
| | access/service | initial | |
| | | req., start | |
| | | Tx timer | |
| | | | |
| PendingI | Successful CC initial answer | Stop Tx | Open |
| | received | timer | |
| | | | |
| PendingI | Failure to send, or temporary | Grant | Idle |
| | error and CCFH equal to | service to | |
| | CONTINUE | end user | |
| | | | |
| PendingI | Failure to send, or temporary | Terminate | Idle |
| | error and CCFH equal to | end user's | |
| | TERMINATE or to | service | |
| | RETRY_AND_TERMINATE | | |
| | | | |
| PendingI | Tx timer expired and CCFH | Terminate | Idle |
| | equal to TERMINATE | end user's | |
| | | service | |
| | | | |
| PendingI | Tx timer expired and CCFH | Grant | PendingI |
| | equal to CONTINUE or to | service to | |
| | RETRY_AND_TERMINATE | end user | |
| | | | |
| PendingI | CC initial answer received | Terminate | Idle |
| | with Result-Code equal to | end user's | |
| | END_USER_SERVICE_DENIED or to | service | |
| | USER_UNKNOWN | | |
| | | | |
| PendingI | CC initial answer received | Grant | Idle |
| | with Result-Code equal to | service to | |
| | CREDIT_CONTROL_NOT_APPLICABLE | end user | |
| | | | |
| PendingI | Failed CC initial answer | Grant | Idle |
| | received and CCFH equal to | service to | |
| | CONTINUE | end user | |
| | | | |
| PendingI | Failed CC initial answer | Terminate | Idle |
| | received and CCFH equal to | end user's | |
| | TERMINATE or to | service | |
| | RETRY_AND_TERMINATE | | |
| | | | |
| PendingI | User service terminated | Queue | PendingI | | | | termination | | | | | event | | | | | | | | PendingI | Change in rating condition | Queue | PendingI | | | | changed | | | | | rating | | | | | condition | | | | | event | | +----------+-------------------------------+-------------+----------+ Table 3: Session-Based Client State Machine for the First Interrogation with CCR +----------+-------------------------------+-------------+----------+ | State | Event | Action | New | | | | | State | +----------+-------------------------------+-------------+----------+ | Open | Granted unit elapses and no | Send CC | PendingU | | | final-unit indication | update | | | | received | req., start | | | | | Tx timer | | | | | | | | Open | Granted unit elapses and | Terminate | PendingT | | | final unit action equal to | end user's | | | | TERMINATE received | service, | | | | | send CC | | | | | termination | | | | | req. | | | | | | | | Open | Change in rating condition in | Send CC | PendingU | | | queue | update | | | | | req., start | | | | | Tx timer | | | | | | | | Open | Service terminated in queue | Send CC | PendingT | | | | termination | | | | | req. | | | | | | | | Open | Change in rating condition or | Send CC | PendingU | | | Validity-Time elapses | update | | | | | req., start | | | | | Tx timer | | | | | | | | Open | User service terminated | Send CC | PendingT | | | | termination | | | | | req. | |
| | | | |
| Open | RAR received | Send RAA | PendingU |
| | | followed by | |
| | | CC update | |
| | | req., start | |
| | | Tx timer | |
| | | | |
| PendingU | Successful CC update answer | Stop Tx | Open |
| | received | timer | |
| | | | |
| PendingU | Failure to send, or temporary | Grant | Idle |
| | error and CCFH equal to | service to | |
| | CONTINUE | end user | |
| | | | |
| PendingU | Failure to send, or temporary | Terminate | Idle |
| | error and CCFH equal to | end user's | |
| | TERMINATE or to | service | |
| | RETRY_AND_TERMINATE | | |
| | | | |
| PendingU | Tx timer expired and CCFH | Terminate | Idle |
| | equal to TERMINATE | end user's | |
| | | service | |
| | | | |
| PendingU | Tx timer expired and CCFH | Grant | PendingU |
| | equal to CONTINUE or to | service to | |
| | RETRY_AND_TERMINATE | end user | |
| | | | |
| PendingU | CC update answer received | Terminate | Idle |
| | with Result-Code equal to | end user's | |
| | END_USER_SERVICE_DENIED | service | |
| | | | |
| PendingU | CC update answer received | Grant | Idle |
| | with Result-Code equal to | service to | |
| | CREDIT_CONTROL_NOT_APPLICABLE | end user | |
| | | | |
| PendingU | Failed CC update answer | Grant | Idle |
| | received and CCFH equal to | service to | |
| | CONTINUE | end user | |
| | | | |
| PendingU | Failed CC update answer | Terminate | Idle |
| | received and CCFH equal to | end user's | |
| | TERMINATE or to | service | |
| | RETRY_AND_TERMINATE | | |
| | | | |
| PendingU | User service terminated | Queue | PendingU |
| | | termination | |
| | | event | |
| | | | |
| PendingU | Change in rating condition | Queue | PendingU | | | | changed | | | | | rating | | | | | condition | | | | | event | | | | | | | | PendingU | RAR received | Send RAA | PendingU | | | | | | | PendingT | Successful CC termination | | Idle | | | answer received | | | | | | | | | PendingT | Failure to send, temporary | | Idle | | | error, or failed answer | | | | | | | | | PendingT | Change in rating condition | | PendingT | +----------+-------------------------------+-------------+----------+ Table 4: Session-Based Client State Machine for Intermediate and Final Interrogations +----------+--------------------------------+------------+----------+ | State | Event | Action | New | | | | | State | +----------+--------------------------------+------------+----------+ | Idle | Client or device requests a | Send CC | PendingE | | | one-time service | event | | | | | req., | | | | | start Tx | | | | | timer | | | | | | | | Idle | Request in storage | Send | PendingB | | | | stored | | | | | request | | | | | | | | PendingE | Successful CC event answer | Grant | Idle | | | received | service to | | | | | end user | | | | | | | | PendingE | Failure to send, temporary | Indicate | Idle | | | error, failed CC event answer | service | | | | received, or Tx timer expired; | error | | | | requested action CHECK_BALANCE | | | | | or PRICE_ENQUIRY | | | | | | | |
| PendingE | CC event answer received with | Terminate | Idle |
| | Result-Code equal to | end user's | |
| | END_USER_SERVICE_DENIED or to | service | |
| | USER_UNKNOWN and Tx timer | | |
| | running | | |
| | | | |
| PendingE | CC event answer received with | Grant | Idle |
| | Result-Code equal to | service to | |
| | CREDIT_CONTROL_NOT_APPLICABLE; | end user | |
| | requested action | | |
| | DIRECT_DEBITING | | |
| | | | |
| PendingE | Failure to send, temporary | Grant | Idle |
| | error, or failed CC event | service to | |
| | answer received; requested | end user | |
| | action DIRECT_DEBITING; DDFH | | |
| | equal to CONTINUE | | |
| | | | |
| PendingE | Failed CC event answer | Terminate | Idle |
| | received or temporary error; | end user's | |
| | requested action | service | |
| | DIRECT_DEBITING; DDFH equal to | | |
| | TERMINATE_OR_BUFFER and Tx | | |
| | timer running | | |
| | | | |
| PendingE | Tx timer expired; requested | Grant | PendingE |
| | action DIRECT_DEBITING | service to | |
| | | end user | |
| | | | |
| PendingE | Failure to send; requested | Store | Idle |
| | action DIRECT_DEBITING; DDFH | request | |
| | equal to TERMINATE_OR_BUFFER | with | |
| | | T flag | |
| | | | |
| PendingE | Temporary error; requested | Store | Idle |
| | action DIRECT_DEBITING; DDFH | request | |
| | equal to TERMINATE_OR_BUFFER; | | |
| | Tx timer expired | | |
| | | | |
| PendingE | Failed answer or answer | | Idle |
| | received with Result-Code | | |
| | equal to END_USER_SERVICE | | |
| | DENIED or to USER_UNKNOWN; | | |
| | requested action | | |
| | DIRECT_DEBITING; Tx timer | | |
| | expired | | |
| | | | |
| PendingE | Failed CC event answer | Indicate | Idle | | | received; requested action | service | | | | REFUND_ACCOUNT | error and | | | | | delete | | | | | request | | | | | | | | PendingE | Failure to send or Tx timer | Store | Idle | | | expired; requested action | request | | | | REFUND_ACCOUNT | with | | | | | T flag | | | | | | | | PendingE | Temporary error; requested | Store | Idle | | | action REFUND_ACCOUNT | request | | | | | | | | PendingB | Successful CC answer received | Delete | Idle | | | | request | | | | | | | | PendingB | Failed CC answer received | Delete | Idle | | | | request | | | | | | | | PendingB | Failure to send or temporary | | Idle | | | error | | | +----------+--------------------------------+------------+----------+ Table 5: One-Time Event Client State Machine +-------+------------------------+--------------------------+-------+ | State | Event | Action | New | | | | | State | +-------+------------------------+--------------------------+-------+ | Idle | CC initial request | Send CC initial answer, | Open | | | received and | reserve units, start Tcc | | | | successfully processed | | | | | | | | | Idle | CC initial request | Send CC initial answer | Idle | | | received but not | with Result-Code != | | | | successfully processed | SUCCESS | | | | | | | | Idle | CC event request | Send CC event answer | Idle | | | received and | | | | | successfully processed | | | | | | | | | Idle | CC event request | Send CC event answer | Idle | | | received but not | with Result-Code != | | | | successfully processed | SUCCESS | | | | | | |
| Open | CC update request | Send CC update answer, | Open | | | received and | debit used units, | | | | successfully processed | reserve new units, | | | | | restart Tcc | | | | | | | | Open | CC update request | Send CC update answer | Idle | | | received but not | with Result-Code != | | | | successfully processed | SUCCESS, debit used | | | | | units | | | | | | | | Open | CC termination request | Send CC termin. answer, | Idle | | | received and | stop Tcc, debit used | | | | successfully processed | units | | | | | | | | Open | CC termination request | Send CC termin. answer | Idle | | | received but not | with Result-Code != | | | | successfully processed | SUCCESS, debit used | | | | | units | | | | | | | | Open | Session supervision | Release reserved units | Idle | | | timer Tcc expired | | | +-------+------------------------+--------------------------+-------+ Table 6: Session-Based and Event-Based Server State Machine8. Credit-Control AVPs
This section defines the Credit-Control AVPs that are specific to the Diameter Credit-Control application and that 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 [RFC7155] and [RFC4004], if the first interrogation is performed as part of the authorization/ authentication process, as described in Section 5.2. The Diameter AVP rules are defined in [RFC6733], Section 4. These AVP rules are observed in AVPs defined in this section. The following table describes the Diameter AVPs defined in the credit-control application, their AVP Code values, types, and possible flag values. The AVP Flag rules ('M', 'V') are explained in [RFC6733], Section 4.1.
+---------------+
|AVP Flag Rules |
Defined |----+-----+----|
AVP in | | |MUST|
Attribute Name Code Section Data Type |MUST| MAY |NOT |
----------------------------------------------------|----+-----+----|
CC-Correlation-Id 411 8.1 OctetString | | M | V |
CC-Input-Octets 412 8.24 Unsigned64 | M | | V |
CC-Money 413 8.22 Grouped | M | | V |
CC-Output-Octets 414 8.25 Unsigned64 | M | | V |
CC-Request-Number 415 8.2 Unsigned32 | M | | V |
CC-Request-Type 416 8.3 Enumerated | M | | V |
CC-Service-Specific- 417 8.26 Unsigned64 | M | | V |
Units | | | |
CC-Session-Failover 418 8.4 Enumerated | M | | V |
CC-Sub-Session-Id 419 8.5 Unsigned64 | M | | V |
CC-Time 420 8.21 Unsigned32 | M | | V |
CC-Total-Octets 421 8.23 Unsigned64 | M | | V |
CC-Unit-Type 454 8.32 Enumerated | M | | V |
Check-Balance-Result 422 8.6 Enumerated | M | | V |
Cost-Information 423 8.7 Grouped | M | | V |
Cost-Unit 424 8.12 UTF8String | M | | V |
Credit-Control 426 8.13 Enumerated | M | | V |
Credit-Control- 427 8.14 Enumerated | M | | V |
Failure-Handling | | | |
Currency-Code 425 8.11 Unsigned32 | M | | V |
Direct-Debiting- 428 8.15 Enumerated | M | | V |
Failure-Handling | | | |
Exponent 429 8.9 Integer32 | M | | V |
Final-Unit-Action 449 8.35 Enumerated | M | | V |
Final-Unit-Indication 430 8.34 Grouped | M | | V |
QoS-Final-Unit-Indication 669 8.68 Grouped | | M | V |
Granted-Service-Unit 431 8.17 Grouped | M | | V |
G-S-U-Pool-Identifier 453 8.31 Unsigned32 | M | | V |
G-S-U-Pool-Reference 457 8.30 Grouped | M | | V |
Multiple-Services- 456 8.16 Grouped | M | | V |
Credit-Control | | | |
Multiple-Services- 455 8.40 Enumerated | M | | V |
Indicator | | | |
Rating-Group 432 8.29 Unsigned32 | M | | V |
Redirect-Address-Type 433 8.38 Enumerated | M | | V |
Redirect-Server 434 8.37 Grouped | M | | V |
Redirect-Server-Address 435 8.39 UTF8String | M | | V |
Redirect-Server-Extension 665 8.64 Grouped | | M | V |
Redirect-Address- 666 8.65 Address | | M | V |
IPAddress | | | |
Redirect-Address-URL 667 8.66 UTF8String | | M | V |
Redirect-Address-SIP-URI 668 8.67 UTF8String | | M | V |
Requested-Action 436 8.41 Enumerated | M | | V | Requested-Service-Unit 437 8.18 Grouped | M | | V | Restriction-Filter-Rule 438 8.36 IPFilterRule| M | | V | Service-Context-Id 461 8.42 UTF8String | M | | V | Service-Identifier 439 8.28 Unsigned32 | M | | V | Service-Parameter-Info 440 8.43 Grouped | | M | V | Service-Parameter-Type 441 8.44 Unsigned32 | | M | V | Service-Parameter-Value 442 8.45 OctetString | | M | V | Subscription-Id 443 8.46 Grouped | M | | V | Subscription-Id-Data 444 8.48 UTF8String | M | | V | Subscription-Id-Type 450 8.47 Enumerated | M | | V | Subscription-Id-Extension 659 8.58 Grouped | | M | V | Subscription-Id-E164 660 8.59 UTF8String | | M | V | Subscription-Id-IMSI 661 8.60 UTF8String | | M | V | Subscription-Id-SIP-URI 662 8.61 UTF8String | | M | V | Subscription-Id-NAI 663 8.62 UTF8String | | M | V | Subscription-Id-Private 664 8.63 UTF8String | | M | V | Tariff-Change-Usage 452 8.27 Enumerated | M | | V | Tariff-Time-Change 451 8.20 Time | M | | V | Unit-Value 445 8.8 Grouped | M | | V | Used-Service-Unit 446 8.19 Grouped | M | | V | User-Equipment-Info 458 8.49 Grouped | | M | V | User-Equipment-Info-Type 459 8.50 Enumerated | | M | V | User-Equipment-Info-Value 460 8.51 OctetString | | M | V | User-Equipment-Info- 653 8.52 Grouped | | M | V | Extension | | | | User-Equipment-Info- 654 8.53 OctetString | | M | V | IMEISV | | | | User-Equipment-Info-MAC 655 8.54 OctetString | | M | V | User-Equipment-Info-EUI64 656 8.55 OctetString | | M | V | User-Equipment-Info- 657 8.56 OctetString | | M | V | ModifiedEUI64 | | | | User-Equipment-Info-IMEI 658 8.57 OctetString | | M | V | Value-Digits 447 8.10 Integer64 | M | | V | Validity-Time 448 8.33 Unsigned32 | M | | V |8.1. CC-Correlation-Id AVP
The CC-Correlation-Id AVP (AVP Code 411) is of type OctetString and contains information to correlate credit-control requests generated for different components of the service, e.g., transport and service level. Whoever allocates the Service-Context-Id (i.e., a unique identifier of a service-specific document) is also responsible for defining the content and encoding of the CC-Correlation-Id AVP.
8.2. CC-Request-Number AVP
The CC-Request-Number AVP (AVP Code 415) is of type Unsigned32 and identifies this request within one session. As Session-Id AVPs are globally unique, the combination of the Session-Id AVP and the CC-Request-Number AVP 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 of the CC-Request-Number AVP to 0 for a credit-control request with a CC-Request-Type AVP of INITIAL_REQUEST (the initial request in a session). The value of the CC-Request-Number AVP should be set to 1 for the first UPDATE_REQUEST, to 2 for the second, and so on until the value for TERMINATION_REQUEST is one more than the value for the last UPDATE_REQUEST. In the case of event charging (when the CC-Request- Type AVP has the value EVENT_REQUEST), the CC-Request-Number AVP should be set to 0 for a credit-control request.8.3. CC-Request-Type AVP
The CC-Request-Type AVP (AVP Code 416) is of type Enumerated and contains the reason for sending the Credit-Control-Request message. It MUST be present in all Credit-Control-Request messages. The following values are defined for the CC-Request-Type AVP (the value of 0 (zero) is reserved): INITIAL_REQUEST 1 This request is used to initiate a credit-control session. It contains credit-control information that is relevant to the initiation. UPDATE_REQUEST 2 This request contains credit-control information for an existing credit-control session. Credit-control requests of this type 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 This request is sent to terminate a credit-control session. It contains credit-control information relevant to the existing session.
EVENT_REQUEST 4 This request is used when there is no need to maintain any credit-control session state in the credit-control server. It contains all information relevant to the service and is the only request of the service. The reason for this request is further detailed in the Requested-Action AVP. The Requested-Action AVP MUST be included in the Credit-Control-Request message when CC-Request- Type is set to EVENT_REQUEST.8.4. CC-Session-Failover AVP
The CC-Session-Failover AVP (AVP Code 418) is of type Enumerated and contains information as to whether moving the credit-control message stream to a backup server during an ongoing credit-control session is supported. In the case of communication failures, the credit-control message streams can be moved to an alternative destination if the credit-control server supports failover to an alternative server. The secondary credit-control server name, if received from the home Diameter AAA server, can be used as an address of the backup server. An implementation is not required to support moving a credit-control message stream to an alternative server, as this also requires moving information related to the credit-control session to the 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 be moved to an alternative destination in the case of a 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 an alternative destination in the case of a communication failure. Moving the credit-control message stream to a backup server MAY require that information related to the credit-control session should also be forwarded to an alternative server.
8.5. CC-Sub-Session-Id AVP
The CC-Sub-Session-Id AVP (AVP Code 419) is of type Unsigned64 and contains the credit-control sub-session identifier. The combination of the Session-Id AVP 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 that no sub-sessions are in use.8.6. Check-Balance-Result AVP
The Check-Balance-Result AVP (AVP Code 422) 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.8.7. Cost-Information AVP
The Cost-Information AVP (AVP Code 423) is of type Grouped, and it is used to return the cost information of a service, which the credit-control client can transfer transparently to the end user. The included Unit-Value AVP contains the cost estimate (always of type "money") of the service in the case of price inquiries, or the accumulated cost estimation in the case of a credit-control session. The Currency-Code AVP specifies in which currency the cost was given. The Cost-Unit AVP specifies the unit when the service cost is a cost per unit (e.g., cost for the service is $1 per minute). When the Requested-Action AVP with the 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 for the requested service, without any reservations 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 reservations into account. The Cost-Information AVP included in the Credit-Control-Answer command with the CC-Request-Type set to EVENT_REQUEST or TERMINATION_REQUEST contains the estimated total cost for the requested service. The Cost-Information AVP is defined as follows (per grouped-avp-def as defined in [RFC6733]): Cost-Information ::= < AVP Header: 423 > { Unit-Value } { Currency-Code } [ Cost-Unit ]8.8. Unit-Value AVP
The Unit-Value AVP is of type Grouped (AVP Code 445) and specifies the cost as a floating-point value. The Unit-Value is a significand with an exponent; i.e., Unit-Value = Value-Digits AVP * 10^Exponent. This representation avoids unwanted rounding off. For example, the value of 2,3 is represented as Value-Digits = 23 and Exponent = -1. The absence of the exponent part MUST be interpreted as an exponent equal to zero. The Unit-Value AVP is defined as follows (per grouped-avp-def as defined in [RFC6733]): Unit-Value ::= < AVP Header: 445 > { Value-Digits } [ Exponent ]8.9. Exponent AVP
The Exponent AVP is of type Integer32 (AVP Code 429) and contains the exponent value to be applied for the Value-Digits AVP within the Unit-Value AVP.
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