Question: In an NDS/IP network, what is the primary function of Security Gateways (SEGs) at the border between security domains?
Option 1: To encrypt user plane data transmitted over the Gi-interface to external IP networks.
Option 2: To enforce the security policy of a security domain towards other SEGs in the destination security domain.
Option 3: To manage the routing of signaling messages within a single security domain.
Option 4: To monitor performance metrics across multiple security domains.
Explanation: SEGs are responsible for enforcing the security policy between different security domains, ensuring the secure exchange of control plane information. This is crucial for maintaining network domain security (NDS) across operator borders. Options 1, 3, and 4 are incorrect because NDS/IP network security does not extend to the user plane, SEGs primarily handle control plane security between domains, and there's no mention of performance monitoring as a primary function of SEGs.