We do not support RSTP/RTP tunneling when re-streaming RTSP. We do support RTSP/RTP tunneling when using an RTSP/RTP encoder such as Wirecast or Quicktime Broadcaster.
We do now support authentication with the most recent patch. The url format is:
rtsp://username:password@domain:port/streamname
If you use the stream name alias package you can hide the username and password behind an alias:
http://community.wowza.com/t/-/47
Charlie