BAR

Technical Explanation

When a UE is in CM-IDLE, the UPF cannot forward downlink packets directly. The Buffering Action Rule (BAR) specifies buffering parameters: maximum buffer duration, maximum packet count, and whether the UPF should send an immediate Downlink Data Notification (DDN) to the SMF to initiate core network paging.

Key Functions

• Configures downlink packet buffering capacity in the UPF for idle UEs
• Specifies buffer retention timers and maximum byte ceilings
• Triggers Downlink Data Notification to SMF prompting cellular paging