Question: What is the primary purpose of introducing a 'party identifier' in the enhanced data structure for IMS Conferencing services, as per 3GPP security standards?
Option 1: To authenticate users joining a conference
Option 2: To encrypt media streams for confidentiality
Option 3: To identify the source of multicast bearer streams at the MRFP (Media Resource Function Processor)
Option 4: To bill users based on their conference participation
Explanation: In the context of IMS Conferencing services, multicasting at the MRFP requires distinguishing between multiple sources of media streams. The 'party identifier' uniquely identifies each bearer stream's source, ensuring proper routing and handling of multicast traffic within the conference setup, crucial for maintaining multimedia communications integrity.