Question: In an MCPTT (Mission Critical Push To Talk) scenario, from the perspective of an Interworking Function (IWF) floor participant, at what point is the MCPTT call considered established, triggering the creation of a media session instance?
Option 1: Upon receiving a SIP INVITE request for the MCPTT call setup.
Option 2: When the application and signalling plane sends the SIP 200 (OK) response.
Option 3: After the media plane negotiation is successfully completed.
Option 4: Once all participants have acknowledged the floor control.
Explanation: The correct answer highlights that from the IWF floor participant's perspective, the MCPTT call establishment is confirmed and thus triggers the creation of a media session instance when the signalling plane indicates success via a SIP 200 (OK) response, signifying successful acknowledgement by all necessary parties.