Question: When does the PCRF report accumulated usage to the AF in a RA-Request (RAR) command with Specific-Action AVP set to USAGE_REPORT, in the context of Sponsored Data Connectivity?
Option 1: When the AF session is terminated by the AF or the PCRF due to IP-CAN session termination.
Option 2: When the PCRF detects that the usage threshold provided by the AF has been reached or the AF disables sponsored data connectivity.
Option 3: When the home operator policy disallows the UE from accessing sponsored data connectivity in a roaming case, and all service data flows of the AF session are terminated.
Option 4: When the PCEF/TDF requests an update for the Sponsored-Connectivity-Data AVP.
Explanation: According to the specified behavior for Sponsored Data Connectivity, the PCRF is required to report accumulated usage to the AF in a RA-Request (RAR) command with Specific-Action set to USAGE_REPORT specifically when it detects that the predefined usage threshold has been met or when the AF explicitly disables sponsored data connectivity. This ensures timely updates for the AF to manage sponsored data allocations effectively.