Question: In a 3GPP-compliant network, how is the interception of content for Multimedia Broadcast Multicast Services (MBMS) typically facilitated, if available?
Option 1: Dedicated MBMS Interception Function (IF) within the Broadcast Multicast Service Centre (BM-SC)
Option 2: Directly by the Cell Broadcast Centre (CBC) for all MBMS transmissions
Option 3: Through the underlying transport bearer interception functionality (e.g., GSN, PDG, or NGN network)
Option 4: Exclusively via a standalone Lawful Interception Gateway (LIG)
Explanation: The correct approach for intercepting MBMS content, as per the provided context, leverages existing infrastructure. Since MBMS is transmitted over transport bearers that are also used for other services, utilizing the "underlying transport bearer interception functionality" (such as that found in GSN - Gateway Serving Node, PDG - Packet Data Gateway, or NGN - Next Generation Network) is the most efficient and integrated method. This approach aligns with the principle of reusing established network functionalities for lawful interception purposes, minimizing the need for service-specific interception solutions.