4 SIP Transfer of Charging Information

29.4583GPPProtocol specificationRelease 8SIP Transfer of IP Multimedia Service Tariff InformationTISPANTS

4.1 Description

4.1.1 General description

The present document specifies the procedures for the realtime transfer of charging information in SIP between a Charge Determination Point (CDP) and a Charge Generation Point (CGP). CDP is a network function that determines which tariff/add-on charge should be applied and inserts the charging information to the appropriate SIP requests or responses, whereas the CGP is a network function that receives the charging information that was added by a CDP.

Example of CDP is a SIP AS at the visited IMS network providing the premium rate service. Example of the CGP is the originating SIP AS at the home IMS network for advice of charge purposes.

The functionality is needed to support the charging of value added services that are charged by the operator of the originating end user, the home IMS operator, in case the operator of the originating end user has no knowledge about the charging information related to these value-added services.

A charge determination and charge generation point of the communication may be located within the network of one operator (single network operator environment) or may be located in different networks of different operators (multi‑operator environment).

The configuration of several charge determination points for one communication is possible. It is assumed that there is only one CGP for the communication.

The transferred charging information represents direct charging information (no pointers to charging data), either in monetary (e.g. currency) units or non-monetary (e.g. meter‑pulse) units.

The following functionality is provided:

i) apply a communication attempt charge for unsuccessful communications;

ii) apply a communication setup charge (once) at start of charging;

  1. apply an initial communication tariff at start of charging and an (optional) next tariff at an absolute time during the communication;

iv) change immediately the current tariff;

v) apply immediately an add-on charge (either a number of non-monetary units or an amount of monetary units) during the communication. This add-on charge is additive and does not change the tariff in force;

vi) differentiation as to whether the charging information is to be used for advice of charge purposes only, or for subscriber charging purposes (which would also allow it to be used for advice of charge purposes);

vii) perform validation (e.g. check range of parameters, check whether a request from a certain network operator can be accepted);

viii) apply a "one time charge" (i.e. non-periodic charge/flat rate) as a minimum communication charge at start of charging;

4.1.2 Network provider option

Not applicable.

4.2 Coding requirements

CDP and CGP shall support the INFO method according to RFC 2976 [2] in support of SIP Transfer of Charging Information.

CDP and CGP shall support multipart MIME content.

The SIP Transfer of Charging Information XML schema, version 1.0, is defined in annex C. The Charging Information XML schema shall be transported as a SIP MIME body. The MIME type for the Charging Information is "application/vnd.etsi.sci+xml". Any SIP message that transports a body with Charging Information shall identify the payload as MIME type "application/vnd.etsi.sci+xml".

4.3 Functional requirements

4.3.1 Overall requirements

a) CGP receives tariff information and shall not send it further, however, the received tariff information can be used for the AoC info provision to the UE.

b) There is only one CGP per service usage and the CGP is always located within the home network of the served subscriber.

c) CDP determines the tariff to be applied or an add on charge, and provides for transfer to the CGP.

d) There can be one or more CDP per service usage. CDP may be located in the originating or in the terminating network.

e) Sending of next tariff information.

A determination point shall not send next tariff information with a switch-over time that is more than 23 h and 45 min after the current time.

f) Format of the Charging Information.

All information issued for the same communication has to be in the same format, i.e. monetary or non-monetary. This needs bilateral agreements between the network operators concerned.

If non-monetary formats are used, the corresponding monetary value of a non-monetary unit needs bilateral agreements between the network operators concerned.

A CDP has to encode the tariff information in a format that can be validated by the receiving CGP.

4.3.2 Procedures at a Charge Determination Point

4.3.2.1 Procedures during communication set-up

4.3.2.1.1 Tariff indication

When a Charge Determination Point has determined that:

– the tariff which has to be activated immediately at start of charging; and/or

– the next tariff which has to be activated at an absolute switch-over time; and/or

– the absolute switch-over time (GMT),

has to be transmitted to the charge generation point, the application process shall issue the Tariff indication.

A Tariff indication may be re-issued during communication set-up phase (i.e. at any time up to the dialog confirmation), replacing previously issued information.

If the tariff is time dependent, then the next tariff and the absolute time at which the current tariff has to be replaced by this next tariff shall be sent. It can be sent together with the current tariff in the initial Tariff indication. The next tariff and the tariff switch-over time shall always be sent together.

The current tariff and the next tariff have the same tariff parameter structure, i.e. a Communication Attempt charge, a Communication Setup charge and a Communication charge (up to a maximum of 4 communication subtariffs).

The tariff format used for the communication is indicated by the first Tariff indication and shall not be changed during the communication.

The following clauses specify the procedures for some specific cases.

4.3.2.1.2 Communication attempt charge

The communication attempt charge is a direct charge, to be charged only for unsuccessful communications.

If a communication attempt charge is relevant to the communication, the communication attempt charge information shall be included in the Tariff indication.

To cover the scenario in the generation point where the received absolute switch-over time has already been reached at the receipt of the Tariff indication or just before start of charging, the communication attempt charge shall also be sent in the first Next Tariff parameter.

In case of monetary-format, the charge amount is indicated by a currency factor multiplied by a currency scale.

In case of non-monetary format, the charge amount is indicated by a number of meter-pulse units.

4.3.2.1.3 Communication set-up charge

The communication setup charge is a direct charge, to be charged once at start of charging.

If communication setup charge is relevant to the communication, the communication setup charge information shall be included in the first Tariff indication.

To cover the scenario in the generation point where the received absolute switch-over time has already been reached at the receipt of the Tariff indication or just before start of charging, the communication setup charge shall also be sent in the first Next Tariff parameter.

In the case of monetary-format, the charge amount is indicated by a currency factor multiplied with a currency scale.

In the case of non-monetary-format the charge amount is indicated by a number of meter-pulse units.

4.3.2.1.4 Communication charge

The communication charge is a direct charge, to be applied at start of charging.

If communication charge is relevant, this information shall be included in the first Tariff indication and before start of charging.

a) Non-monetary-format.

In case of non-monetary-format, the charge amount is indicated by a number of meter-pulse units to be applied per time unit. The Communication charge is free when its value is zero.

b) Monetary-format.

In case of monetary-format, the charge amount per time unit is indicated by a currency factor multiplied by a currency scale. The communication charging is free of charge when the product is zero.

NOTE: With the currency-format only one fixed time unit is used. This fixed time unit is one second, according to RFC 4006 [3].

c) Communication charge sequence.

The communication charge may be a sequence of up to 4 communication subtariffs. Except for the last subtariff, each subtariff shall be limited by its tariff duration. The last (or single) subtariff of the sequence may be either unlimited (tariff duration = 0) or limited.

At expiry of the tariff duration timer of the last (single) communication subtariff of the communication charge sequence, the following options are possible:

– the communication charge sequence is re-applied; or

– the communication charge sequence is not re-applied.

The chosen option is indicated in the tariffControlIndicators.

If a communication charge sequence is relevant to the communication, the complete sequence shall be provided.

d) Absolute switch-over time.

The absolute switch-over time is the time at which the current tariff has to be replaced by the next tariff.

The next tariff and the tariff switch-over time shall always be provided together.

e) Minimum Communication Charge at Start of Charging.

To apply a minimum communication charge in case of non-monetary format, the first subtariff of the sequence is defined with N pulses, a duration which corresponds to the required duration and a time interval equal to zero.

To apply a minimum communication charge in case of monetary format, the first subtariff is defined with N currency units and a duration which corresponds to the required duration. A flag in CommunicationChargeCurrency (subTariffControl) indicates whether the tariff is a "one time charge" for the minimum communication charge or not.

4.3.2.2 Procedures after start of charging

The following clauses and clause 4.3.2.3 specify the procedures for some specific cases.

4.3.2.2.1 Change current tariff

The current tariff can be changed by issuing a Tariff indication with the new current tariff.

4.3.2.2.2 Add-on charging information

If a charge determination point determines that a certain amount of charge has to be added, the application process issues an Add-on-charge indication. The current tariff is not changed.

An Add-on-charge indication is allowed after start of charging only.

The charge is either in non-monetary format or in monetary format.

The add-on charge in non-monetary-format is a number of meter-pulse units. The add-on charge in monetary format is indicated by the currency factor multiplied by the currency scale.

4.3.2.3 Subsequent Tariff indications

In addition to the first Tariff indication, the application process in a determination point issues subsequent Tariff indication during the communication in the following cases:

a) The current tariff is changed. A Tariff indication with the new current tariff t has to be issued immediately.

b) The next tariff and its tariff switch-over time were not issued at communication setup. This exceptional case occurs when the switch-over time was more than 23 h and 45 min after the moment the communication is set-up. A Tariff indication with the next tariff and the corresponding switchover time has to be issued at least before the switchover time.

4.3.3 Procedures at the charge generation point

The following general rule applies: Currently stored information related to one network operator is replaced by information related to this operator received subsequently.

4.3.3.1 Procedures during communication set-up

4.3.3.1.1 Tariff indication

The receipt of the Tariff indication indicates:

– the tariff which has to be activated immediately at start of charging; or

– the next tariff which has to be activated at an absolute switch-over time; or

– the absolute switch-over time.

A Tariff indication may be received more than once during communication set-up phase (i.e. at any time up to the dialog confirmation), replacing previously received information.

If the tariff is time dependent, then the next tariff and the absolute time at which the current tariff has to be replaced by this next tariff will be received. They can be received together with the current tariff in the initial Tariff indication.

The current tariff and the next tariff have the same tariff parameter structure, i.e. a communication attempt charge, a communication setup charge and a communication charge (up to a maximum of 4 communication subtariffs). The tariff parameters have either the non-monetary format or the monetary format. The tariff-format used for the communication is indicated by the first Tariff indication and shall not be changed during the communication.

Validation shall be performed (e.g. check of range of parameters, check of network identification).

The following clauses specify the procedures for some specific cases.

4.3.3.1.2 Communication attempt charge

The communication attempt charge is a direct charge, to be charged only for unsuccessful communications.

If a communication attempt charge is relevant to the communication, the communication attempt charge information shall be included in the Tariff indication.

In the case of monetary-format, the charge amount is indicated by a currency factor multiplied by a currency scale. The communication attempt charging shall not be performed if the product is zero or the parameter is not present.

In the case of non-monetary-format, the charge amount is indicated by a number of meter-pulse units. The communication attempt charging shall not be performed if the value is zero or the parameter is not present.

4.3.3.1.3 Communication setup charge

The communication setup charge is a direct charge, to be charged once at start of charging.

If a communication setup charge is relevant to the communication, the communication setup charge information is included in the first Tariff indication.

In the case of monetary-format, the charge amount is indicated by a currency factor multiplied with a currency scale. The communication setup charging shall not be performed when the product is zero or the parameter is not present.

In the case of non-monetary-format the charge amount is indicated by a number of meter-pulse units. The communication setup charge shall not be performed when the number is zero or the parameter is not present.

4.3.3.1.4 Communication charge

The communication charge is a direct charge, to be applied at start of charging.

As part of the Current Tariff, the Communication Tariff is applied immediately at start of charging.

As part of the Next Tariff, the Communication Tariff is applied at the absolute time indicated by the absolute switch‑over time parameter. The switch procedure is a network matter.

If the absolute switch-over time given in the Tariff indication is already passed, then the communication charge of the next tariff instead of the current tariff shall immediately be applied (see also clause 4.3.1 b).

a) Non-monetary-format.

In case of non-monetary-format, the charge amount is indicated by a number of meter-pulse units to be applied per time unit. The communication is free of charge when its value is zero.

b) Monetary-format.

In case of monetary-format, the charge amount per time unit is indicated by a currency factor multiplied by a currency scale. The communication is free of charge when the product is zero.

NOTE: With the currency-format only one fixed time unit is used. This fixed time unit is one second, according to RFC 4006 [3].

c) Communication charge sequence.

The communication charge may be a sequence of up to 4 communication subtariffs. Except for the last subtariff, each subtariff shall be limited by its tariff duration. The last (or single) subtariff of the sent sequence may be either unlimited (tariff duration = 0) or limited.

Initially, charging shall use the first subtariff. At expiry of the tariff duration timer, the subsequent subtariff shall be applied.

At expiry of the tariff duration timer of the last (single) communication subtariff of the communication charge sequence, the following options are possible:

– the communication charge sequence is re-applied; or

– the communication charge sequence is not re-applied.

The option to be applied is indicated in the tariffControlIndicators.

If a communication charge sequence is relevant to the communication, the complete sequence shall be provided.

When the communication charge sequence is not re-applied, the following network provider option exists: either the communication continues "free of charge" or the communication is released.

d) Absolute switch-over time.

The absolute switch-over time is the time at which the current tariff has to be replaced by the next tariff. In a multi-operator environment, the procedures of how the subtariffs of the next tariff are applied are subject of bilateral or multilateral agreements.

e) Minimum communication charge at start of charging.

To apply a minimum communication charge in case of pulse format, the first subtariff of the sequence shall defined with N pulses, a duration which corresponds to the required duration and a time interval equal to zero.

To apply a minimum communication charge in case of currency format, the first subtariff shall be defined with N currency units and a duration which corresponds to the required duration. A flag in CommunicationChargeCurrency (subTariffControl) indicates whether the tariff is a "one time charge" for the minimum communication charge or not.

4.3.3.2 Procedures after start of charge

If the communication setup charge is applied, all following received communication attempts and communication setup charges shall be ignored.

The following clauses and clause 4.3.2.4 specify the procedures for some specific cases.

4.3.3.2.1 Change current tariff

a) On receipt of the Tariff indication with the new tariff, the current tariff shall be changed

After successful validation (e.g. check of range of parameters, check of network identification), the new current tariff shall immediately be applied to the communication according to the following two tariff change procedures:

– tariff change without restart of the charging process (see b));

– tariff change with restart of the charging process (see c)).

Which immediate tariff change procedure shall be used is indicated in the ChargingContolIndicators by "immediateChangeOfActuallyAppliedTariff": value 1 means "with restart", value 0 means "without restart".

b) Tariff Change without restart of the charging process.

The charging process for the actual communication shall be continued with the new current tariff. I.e. the tariff change procedure is the same as the one which is performed at a tariff switchover from the current to the next tariff. This means that:

– at the change of a tariff sequence, the new applied subtariff of the new tariff sequence is retrieved via the elapsed communication duration;

– at the change of a non-periodic tariff, the new non-periodic tariff is not applied (no double counting);

– the new communication attempt and communication setup charge are not applied.

c) Tariff Change with restart of the charging process.

The charging process with the actual current tariff shall be closed and restarted with the new current tariff. This means that:

– at the change of a tariff sequence, the charging process restarts with the first communication subtariff of the new tariff sequence;

– at the change of a non-periodic tariff, the new non-periodic tariff is applied;

– the new communication attempt and communication setup charge are not applied.

d) In a multi-operator environment, the procedures of how the subtariffs of the next tariff are applied are subject of bilateral or multilateral agreements.

4.3.3.2.2 Add-on charging information

On receipt of the Add-on-charge indication, the given amount of charge has to be added. The current tariff shall not be changed.

An Add-on-charge indication is allowed after start of charging only.

The charge is either in non-monetary format or in monetary format.

The add-on charge in non-monetary-format is a number of meter-pulse units. The add-on charge in monetary format is indicated by the currency factor multiplied by the currency scale.

4.3.3.3 Subsequent Tariff indications

In addition to the first Tariff indication, subsequent Tariff indications during the communication may be received in the following cases:

a) The current tariff has to be changed. A Tariff indication with the new current tariff together with the next tariff and its switch-over time will be received.

b) The next tariff and its tariff switch-over time were not received at communication setup. A Tariff indication with the next tariff and the corresponding switchover time will be received before the switchover time.

4.3.4 Handling of identifiers

The initial indication, i.e. either a Tariff indication or an Add-on-charge indication, issued by the application process in a charge determination point shall contain the originationIdentification A.

The initial acknowledgement (i.e. the first Tariff/Add-on-charge response) to this initial (Tariff/Add-on-charge) indication (with originationIdentification and without destinationIdentification) issued by the application process in the generation point shall contain the originationIdentification B and the destinationIdentification A in order to allow mapping between the sending and receiving direction.

The destinationIdentification A equals the originationIdentification A, and the destinationIdentification B equals the originationIdentification B.

All subsequent Tariff and Add-on-charge indications associated with the same tariff determination instance contain the originationIdentification A and destinationIdentification B. All subsequent Tariff and Add-on-charge responses associated with the same tariff determination instance shall contain the originationIdentification B and destinationIdentification A.

4.4 Signalling requirements

4.4.1 General

When sending tariff information, the CDP shall encode this information according to the XML-schema defined in annex C and send it to the CGP. In addition, for this MIME body the AS:

– shall set the Content-Type header to "application/vnd.etsi.sci+xml" and set the Content-Disposition to "render" with the "handling" parameter set to "optional".

In the case the Charging information is transported in a message that is forwarded by CDP that contains already a content body, CDP shall generate a multipart/mixed MIME body containing two sub-parts:

– one with the Charging information; the Content-Type and Content-Disposition of this sub-part should be coded as specified for non-multipart bodies;

– one with the received body; headers describing the content of the received SIP message (e.g. Content-type) should be moved into the headers of the this subpart.

4.4.2 Procedures during communication set-up

4.4.2.1 Procedures at the CDP

When an INVITE request is received, the CDP operates as a routing B2B UA as specified in clause 5.7.5 of
ES 283 003 [4] and includes the tariff information in the content body of a reliable 1xx provisional response, or in the content body of a 200 OK.

4.4.3 Procedures after start of charging

4.4.3.1 Procedures at the CDP

The CDP operates as a routing B2B UA as specified in clause 5.7.5 of ES 283 003 [4] and may send tariff information at any moment during the active phase of the communication. When sending the tariff information, the CDP shall include the tariff information in the content body of a mid-dialog request, a mid-dialog response or in the content body of a 200 OK response forwarded by the CDP or of an INFO request generated by the CDP.

4.5 Interaction with other services

Not applicable.

4.6 Interactions with other networks

4.6.1 Interaction with PSTN/ISDN

In case of interaction with networks which do not provide tariff information in the signalling system, the tariff information shall be discarded and the communication shall continue according to the basic call procedures.

The elements and types of the SIP Transfer of Charging Information XML schema, version 1.0 (defined in annex C), shall be mapped to/from the regarding elements and types of the Charging ASE defined in clause 8 of ES 201 296 [6], as described in table 1. When the MGCF is able to interwork the ISUP charging ASE to a XML instance, the MGCF shall send to the ISDN network an ISUP charging acknowledgment "accepted". Was the interworking not successful, the MGCF acts as described in clause 6.3.6 of ES 201 296 [6] or no acknowledgement is sent.

Table 1: Mapping of Tariff elements

SIP Transfer of Charging Information

XML schema

ISUP Signalling aspects of Charging

Charging ASE

  • messageType

– crgt

– aocrg

  • chargingMessageType

– crgt

– aocrg

ChargingTariffInformationType

  • chargingControlIndicators
  • chargingTariff

– tariffCurrency

– tariffPulse

  • originationIdentification
  • destinationIdentification

currency

ChargingTariffInformation

  • chargingControlIndicators
  • chargingTariff

– tariffCurrency

  • – tariffPulse
  • originationIdentification
  • destinationIdentification
  • currency

AddOnChargeInformationType

  • chargingControlIndicators
  • addOnCharge

– addOnChargeCurrency

– addOnChargePulse

  • originationIdentification
  • destinationIdentification

currency

AddOnChargeInformation

  • chargingControlIndicators
  • addOnCharge

– addOnChargeCurrency

– addOnChargePulse

  • originationIdentification
  • destinationIdentification

currency

TariffSwitchPulseType

  • nextTariffPulse

tarffSwitchOverTimer

TariffSwitchPulse

  • nextTariffPulse

tarffSwitchOverTimer

CommunicationChargePulseType

  • pulseUnits
  • chargeUnitTimeInterval

TariffDuration

CommunicationChargePulse

  • pulseUnits
  • chargeUnitTimeInterval

TariffDuration

TariffPulseFormatType

  • communicationChargeSequencePulse
  • tariffControlIndicators
  • callAttemptChargePulse

callSetupChargePulse

TariffPulseFormat

  • communicationChargeSequencePulse
  • tariffControlIndicators
  • callAttemptChargePulse

callSetupChargePulse

CommunicationChargeCurrencyType

  • currencyFactorScale
  • tariffDuration

subTariffControl

CommunicationChargeCurrency

  • currencyFactorScale
  • tariffDuration

subTariffControl

TariffSwitchCurrencyType

  • nextTariffCurrency

tariffSwitchOverTimer

TariffSwitchCurrency

  • nextTariffCurrency

tariffSwitchOverTimer

TariffCurrencyFormatType

  • communicationChargeSequence Currency
  • tariffControlIndicators
  • callAttemptChargeCurrency

callSetupChargeCurrency

TariffCurrencyFormat

  • communicationChargeSequence Currency
  • tariffControlIndicators
  • callAttemptChargeCurrency

callSetupChargeCurrency

CurrencyFactorScaleType

  • currencyFactor

currencyScale

CurrencyFactorScale

  • currencyFactor

currencyScale

TariffPulseType

  • currentTariffPulse

tariffSwitchPulse

TariffPulse

  • currentTariffPulse

tariffSwitchPulse

TariffCurrencyType

  • currentTariffCurrency

tariffSwitchCurrency

TariffCurrency

  • currentTariffCurrency

tariffSwitchCurrency

ChargingControlIndicatorsType

  • immediateChangeOfActuallyApplied Tariff

delayUntilStart

ChargingControlIndicators

  • immediateChangeOfActuallyApplied Tariff

delayUntilStart

ChargingReferenceIdentificationType

  • networkIdentification

referenceID

ChargingReferenceIdentification

  • networkIdentification

referenceID

bitType

STRING

eightBitType

OCTET STRING (size (1))

sixteenBitType

OCTET STRING (size (2))

NetworkIdentificationType

NetworkIdentification

CurrencyType

EUR

USD

CNY

Currency

Euro

uSDollar

chineseYuan

CurrencyFactorType

CurrencyFactor

CurrencyScaleType

CurrencyScale

TariffDurationType

TariffDuration

4.6.2 Interaction with PSTN/ISDN Emulation

For Further Study.

4.6.3 Interaction with external IP networks

The procedures of ES 283 003 [4] shall apply.

Annex A (informative):
Signalling flows

NOTE: The UNI AOC messages (to the left of the CGP) are out of scope of the present document and are shown for explanation reasons.

Figure 1: Transfer of Tariff information during communication set-up

Figure 1 gives an example for transfer of tariff information during the communication set-up phase. When an INVITE request is received, the CDP includes the Charging information in the content body of a reliable 1xx provisional response, in this example the 183 Session progress response. The tariff information includes the current tariff T1, the next tariff T2, and the absolute switch-over time 10 h and 00 min.

The CGP applies T1 when the dialog is confirmed after the reception of the 200 OK. At 10 h and 00 min the CGP switches to T2.

Figure 2: Transfer of Add-on-charge information

Figure 2 gives an example for transfer of add-on-charge information after start of charging. The CDP includes the Charging information in the content body of an INFO request.

After the reception of the INFO request the CGP applies the add-on charge.

Figure 3: Immediate tariff change without restart of the charging instance

Figure 3 gives an example for an immediate tariff change without a restart of the charging instance. After start of charging, the CDP includes the Charging information in the content body of an INFO request. The tariff information includes the new current tariff T2, which is a tariff sequence with the sub-tariffs T21 (duration 1 h) and T22 (duration unlimited), and the indication that no restart shall be applied.

After the reception of the INFO request the CGP applies T22, because T22 is valid 1 h and 30 min after communication start.

Figure 4: Immediate tariff change with restart of the charging instance

Figure 4 gives an example for an immediate tariff change with a restart of the charging instance. After start of charging, the CDP includes the Charging information in the content body of an INFO request. The tariff information includes the new current tariff T2, which is a tariff sequence with the sub-tariffs T21 (duration 1 h) and T22 (duration unlimited), and the indication that a restart shall be applied.

After the reception of the INFO request the CGP restarts the charging instance and applies T21 for 1 h, and then switches to T22.

Annex B (informative):
SIP Transfer of Charging Information parameters