Question: In a Policy and Charging Control (PCC) architecture, when is a CCR (CC-Request) command with the 'R' bit set in the Command Flags field sent from the TDF (Traffic Detection Function) to the PCRF (Policy and Charging Rules Function), aside from requesting ADC rules?
Option 1: During initial network attachment of a User Equipment (UE)
Option 2: In response to a change in the UE's Quality of Service (QoS) profile
Option 3: Following receipt of a corresponding RAR (Re-Auth Request) command from the PCRF for TDF session termination
Option 4: Periodically, as part of a keep-alive mechanism between TDF and PCRF
Explanation: This option is correct because one of the scenarios where a CCR command with the 'R' bit set is sent from the TDF to the PCRF is indeed in case of TDF session termination, following receipt of the corresponding RAR command from the PCRF. This highlights an important aspect of PCC, which is the coordination between TDF and PCRF for managing sessions and applying rules appropriately during termination.