Question: In an IMS (IP Multimedia Subsystem) architecture, what is the recommended configuration regarding Network Address Translation (NAT) between the GGSN/P-GW and the P-CSCF to avoid specific issues?
Option 1: A NAT must be present for security enhancements.
Option 2: The use of NAT is optional but recommended for traffic optimization.
Option 3: No NAT should exist (or its existence should be transparent) to prevent potential keep-alive message overhead.
Option 4: A double NAT setup is required for enhanced privacy.
Explanation: The absence of a NAT (or keeping its existence transparent towards the UE) between the GGSN/P-GW and the P-CSCF is crucial. This configuration prevents issues such as increased keep-alive message traffic, which could lead to unnecessary battery drain on User Equipment (UE). This setup ensures efficient communication without imposing additional, potentially draining, network maintenance traffic on the UE.