Echo application The echo application echos the voice back to the caller. The echo application resides in the core/plug-in directory. Its purpose is mainly testing the Media Server and the total network delay. If the echo module is compiled with the STAR_SWITCHES_PLAYOUTBUFFER option (enabled by default), the star key pressed on the phone switches between adaptive playout buffer and fifo playout buffer. Thus the effect of the adaptive playout buffering can easily be verified.
The echo application is also a test application for RFC4028 SIP Session Timers. For this, enable_session_timer=yes needs to be set in echo.conf