Question: What is a mandatory function for an Interworking Function (IWF) when performing the controlling role in Mission Critical Push To Talk (MCPTT) media plane control interworking with Land Mobile Radio (LMR) systems?
Option 1: Providing a floor request queue to MCPTT clients
Option 2: Supporting only off-network mode floor control protocol elements
Option 3: Acting solely as a media distributor without floor control interface
Option 4: Supporting negotiating media plane control channel media level attributes
Explanation: When an IWF performs the controlling role, it must support key functionalities that enable effective media plane control. Supporting the negotiation of media plane control channel media level attributes is critical for ensuring compatibility and efficient communication between MCPTT and LMR systems, facilitating seamless interactions between different communication systems.