The FMS URL should point to an application that is configured for live streaming and cupertino packetizing.
You can use any stream name. There is no significance to the extension of a stream name in a live encoder. It can have no extension. Some add .sdp or .mp4 extension, which is no problem but has no affect either. But whatever you name the stream is what you playback. If it is myStream.sdp then you will always use that full name to playback, in all clients.
What does have an affect is adding mp4: prefix to the stream name in the encoder. If the video is h.264 and you are using StreamType “live-record” then adding the mp4: prefix will instruct Wowza to record to a .mp4 container. So FMLE stream name “mp4:myStream” will be recorded to a file named myStream.mp4.
Richard