2.1 ZBA Functionality

ZBA can inspect ingress Gy/Ro Request and Answer messages to verify if subscribers who might have zero balance accounts must be blocked (based on answer messages). It uses MSISDN to check the subscriber’s status in UDR.

It forwards the ingress Gy/Ro Request messages to the OCSs if the subscriber’s status is not in the "blocking" state.

Subscribers might have zero balance, but their messages might be routed to OCS if the number of Zero Balance events detected is less than a configured threshold during a configured detection interval.

ZBA blocks subscribers whose number of Zero Balance events has exceeded the configured threshold within the configured detection interval and generates a response message (CCA-I/E) on behalf of the OCS when a subscriber is blocked.