When the credit of a prepaid subscriber is exhausted, as specified in the 3GPP Diameter spec for Gy interface (32.229), the OCS can instruct the PGW to redirect the user traffic to a TopUp server.
It is done by the OCS by setting the value of the Final-Unit-Action AVP to the Redirect value (1) and providing the Redirect-Server AVP in the CCA (Credit Control Answer) Diameter message.
Are we talking about standard HTTP redirection?
Can this traffic redirection work in case of HTTPS user traffic?