The B2BUA IEC charging features define immediate event charging for Sentinel SIP as a B2BUA.
Description
Feature script name |
B2BUAIECPreFeature, B2BUAIECPostFeature |
|---|---|
Applicable contexts |
SIP service |
Prerequisite features |
B2BUA |
Feature execution points |
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The B2BUA IEC pre and post features cover event charging using a charge/refund model. The features are responsible for:
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creating the reservation charging instance (
B2BUAChargingFeatureUtil.DEFAULT_IEC_CHARGING_INSTANCE) and default session counter on an initial SUBSCRIBE, MESSAGE, OPTIONS, or PUBLISH request -
instructing the charging manager to send a direct debit to the OCS
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detection of message nondelivery conditions and refunding as necessary
The general use case is that a chargeable message — a SUBSCRIBE, MESSAGE, OPTIONS, or PUBLISH — will be B2BUA’d through Sentinel. The IEC post feature will trigger a direct debit, then allow delivery of the message. If a response to the B2BUA’d message is received which indicates non-delivery, the amount debited will be refunded.
For a high level overview of Sentinel charging see Sentinel SIP Charging Architecture
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During any credit check, Sentinel automatically ensures all incoming messages are queued in the SLEE until the CCA (or a timeout) is received; in other words, no further network events will be delivered to Sentinel or processed until the credit check is complete. Currently, Sentinel for SIP only supports one charging instance per Sentinel session, though this instance may have multiple session counters. |
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All of Sentinel for SIP’s charging features make use of Sentinel’s comprehensive charging API — see Using the SIP Charging Manager |
Session state inputs and outputs
Inputs
| Name | Format | Description | Behaviour if null/invalid |
|---|---|---|---|
SentinelSelectionKey |
selection key (for example, |
For selecting mappers |
Increment InputParameterErrors Common cleanup actions |
CurrentSipFeatureExecutionPoint |
Enum value |
Used to classify the triggering event |
N/A |
B2BUAChargingCounterAddress |
key/value pairs identifying the session charged service |
Determines which counter the feature will update with charging data (the IEC features only treat one counter as the session charging counter at a time). Also see Outputs. |
No-op unless initial request |
LatestOcsAnswer |
Last received CCA |
Passed through to a charging mapper to generate the session counter values |
Exception thrown, if the feature is expecting a response from the OCS. Otherwise ignored. |
RequestUnitsServiceSpecific |
Non-negative long |
The number of pending requested units |
N/A |
Outputs
| Name | Format | Description |
|---|---|---|
B2BUAChargingCounterAddress |
key/value pairs identifying the session charged service |
Mapped from initial incoming chargeable event request in SIP initiated sessions to determine the default session counter against which the units will be charged. |
Charging API interactions
The charging API interactions fall under the following categories:
-
charging instructions issued on the
B2BUAChargingFeatureUtil.DEFAULT_IEC_CHARGING_INSTANCEitself -
updates made to all counters on the charging instance, mainly limited to updates from CCAs.
-
complete implementation of event based charging on the default counter.
Interaction with the default charging instance
Initialisation
When the pre-feature is first triggered on an incoming event request, it creates the default IEC charging instance, under the name B2BUAChargingFeatureUtil.B2BUA_IEC_CHARGING_INSTANCE. It then maps the initial event request to a session counter address written to the session state field B2BUAChargingCounterAddress. This is the default session counter on which all IEC based charging is performed.
Initial debit
On any trigger other than an incoming chargeable event request, both features check whether the B2BUAChargingFeatureUtil.DEFAULT_IEC_CHARGING_INSTANCE has been initialised. The first step is to check the instance exists in the ChargingManager, then that the instance has a session counter with the address specified in session state B2BUAChargingCounterAddress. If either check fails, the feature ends immediately on the assumption that IEC is not enabled.
The pre feature will instruct the charging instance to send a direct debit message to the OCS.
The post feature will set the pending requested units and suspend the called party leg until the OCS authorises the call.
Interaction with all session counters
When a CCA is received, all counters on the ChargingInstance will be processed according to the algorithm outlined in Counter Update Algorithm Pseudo Code. The pre feature will clear the pending requested units on all session counters.
When charging using a non-default counter, another feature will need to set reported used and pending requested units on the counters as needed.
Interaction with the default session counter
The default IEC session counter is fully managed by the IEC pre and post features. Generally speaking, user features need not interact directly with this counter.
Setting pending requested units on the default counter
When the post feature is triggered on a chargable event, the pending requested units will be set to the value of RequestUnitsServiceSpecific in session state, unless they have already been set to a non-zero value. If the pending requested units value is non-zero, it will not be overwritten.
Mappers
This feature uses two mappers:
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The first converts the initial SIP request to a SessionCounterAddress.
The default implementation is SipRequestToSessionCounterAddress:// a mapper that takes a {{SipRequest}} and generates a {{SessionCounterAddress}}. final Mapper<SentinelSipSessionState> mapper = getMapperLibrary().findMapper( getSessionState().getSentinelSelectionKey(), SipRequest.class, SessionCounterAddress.class, mappingPoint); -
The second mapper converts a CCA into a list of session counters.
The default implementation is CCAtoSessionCounterList:// a mapper that takes a {{CreditControlAnswer}} and generates a {{List<SessionCounter>}}. final Mapper<SentinelSipSessionState> mapper = getMapperLibrary().findMapper( getSessionState().getSentinelSelectionKey(), CreditControlAnswer.class, List.class mappingPoint);
