Description

Feature name

USSD Callback

Applicable contexts

USSD service

Prerequisite features

None

The USSD Callback feature allows a subscriber to request via USSD that Sentinel set up a call between themselves and another party. The call will proceed according to the normal MOC session plan including SCUR charging, credit check, all MOC features and feature execution points. The call protocol is CAPv4.

The first step is to validate the received additional arguments for the USSD Callback feature, which are submitted via the ‘AdditionalArgument’ session state field. They must contain the CdPA argument, which however is not validated. If there are no additional arguments present the feature will report featureFailedToExecute and cease execution.

If validation succeeds, an HTTP call setup request is sent to a configurable host. In case of any error the feature reports featureFailedToExecute and takes no further action.

If the HTTP response code is ‘200 Ok’ its content string is checked to be non-empty and is then stored into the ‘ResponseMessage’ session state field. If it is an error response or invalid, the feature reports featureFailedToExecute to the core. In any case, feature execution is complete. It is then up to the HTTP server to establish the call through Sentinel.

Session state inputs and outputs

Inputs

Name Type Format Description Behaviour if null/invalid

AdditionalArgument

String

CdPA parameter

Detach from HTTP Aci if required
Report featureFailedToExecute, featureHasFinished

MSISDN

String

MSISDN

Calling party address

Dependent on behaviour of HTTP host

Outputs

Name Type Format Description

MAPResponseErrorType

int

error code

Indicates the failure mode of USSD Balance Enquiry to the USSD service

ResponseMessage

String

Plain text (e.g. “Failed to setup call (SR)”)

A response message containing either an error message or the HTTP response content

Error scenarios

Scenario Handling

Sessionstate AdditionalArgument is null

Set sessionstate MAPResponseErrorType to MAP_USSD_ERROR_DATA_MISSING
Report featureFailedToExecute
Detach from HTTP Aci if required

No USSDCallbackConfiguration

Set sessionstate ResponseMessage to “Failed to setup call (SR)”
Report featureFailedToExecute
Detach from HTTP Aci if required

HTTP Error or IOException retrieving HTTP response content

Set sessionstate ResponseMessage to “Failed to setup call (Error)”
Report featureFailedToExecute
Detach from HTTP Aci if required

HTTP response timeout

Set sessionstate ResponseMessage to “Failed to setup call (Timeout)”
Report featureFailedToExecute
Detach from HTTP Aci if required

Feature responses

Response Reason

featureFailedToExecute

invalid USSD parameters, failed to send call setup request, received empty HTTP message or error response, response timeout etc

featureHasFinished

feature has finished

Format of the HTTP call setup request

The call setup request format is not configurable. However the URL Host and Port are configurable.

http://<HOST>:<PORT>/sentinel-ss7?cgpa=<CGPA>&cdpa=<CDPA>

CGPA and CDPA are read from session state fields MSISDN and AdditionalArgument respectively, and are determined by the USSD service itself (from the initiating USSD request).

Configuration

USSDCallback configuration:

Parameter Type Description

CallbackRequestHost

String

The host to which the callback HttpRequest shall be sent

CallbackRequestPort

Integer

The port to which the callback HttpRequest shall be sent

Configuration profile naming

Configuration Profile Table Name Description Profile Naming

USSDServiceCallbackConfigurationTable

USSDCallback feature configuration

USSDServiceCallbackConfiguration
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Sentinel Express Version 2.7.0