Question: When a PSS client wants to terminate the streaming of a specific media stream in an ongoing session, what should it include in the PLAY request's 'Switch-Stream' header?
Option 1: The URL of the new media stream to be initiated
Option 2: Only the URL of the media stream to be torn down (as the old media stream)
Option 3: URLs for all remaining media streams in the session
Option 4: No URL, indicating a pause for all media streams
Explanation: According to the protocol for managing ongoing sessions, when a PSS client wishes to terminate a specific media stream, it must send a PLAY request with a 'Switch-Stream' header that specifically identifies the media stream to be terminated by its URL. This approach ensures that only the targeted stream is stopped without interrupting other streams in the session.