Typical call flow

 

USSD Message Type

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Process unstructured supplementary services Request (PSSR):-

First message sent in case of Mobile Initiated (MI)USSD to initiate USSDsession. The response for this message from GW is USSR/USSN.

Process unstructured supplementary services Request ACK (PSSR ACK):-

This message is the last message sent from GW to a SpecificPSSR to close the USSD session.

Unstructured supplementary services request (USSR):-

This message is used to send the menu to subscriber. Incaseof Network Initiated USSD, this is the first message. Subscriber can reply to this message withappropriate option.(1/2/3).

Unstructured supplementary services request ACK (USSR ACK):-

This message contains the subscriber¶s response to the menu sent in USSR.