Question: In a routed RG with NAT mode, how does the Policy Control and Charging Rules Function (PCRF) retrieve usage monitoring related information for allocating a usage threshold to an IP-CAN session?
Option 1: Directly from the PCEF/IP-Edge using the IP address of the RG.
Option 2: From the Serving and Policy Repository (SPR) using the device's MAC address provided over Gx.
Option 3: Through periodic reports sent by the User Equipment (UE) via the S1-U interface.
Option 4: From the SPR using the subscriber-id provided over Gx.
Explanation: In a routed Residential Gateway (RG) with Network Address Translation (NAT) mode, since multiple devices share the same public IP address, the PCRF relies on subscriber-specific identifiers to manage usage thresholds. The correct approach involves using the subscriber-id provided over the Gx interface to retrieve relevant information from the Serving and Policy Repository (SPR), ensuring accurate allocation of usage thresholds to each IP-CAN session or Monitoring Key (MK), even in NAT environments where public IPs are shared.