Question: What is the primary purpose of deploying Inter PLMN User Plane Security (IPUPS) functionality at the border of a network?
Option 1: To enhance user experience for roaming subscribers
Option 2: To optimize traffic routing between PLMNs
Option 3: To provide additional billing and charging capabilities
Option 4: To protect the network from invalid inter-PLMN N9 traffic
Explanation: The IPUPS functionality is designed to forward GTP-U packets only if they belong to an active PDU Session and are not malformed, thereby protecting the network from potential security threats.