Kernel has to be recompiled.
It works both with incoming and outcoming calls. A public NetMeeting client can call a host, belonging to a private LAN, located behind a NAT router and a private NetMeeting client can call a public NetMeeting host. In both situations we have RTP audio and video packets flowing in the two directions. We tested also a Linux application Voxilla on private and public hosts. It works both with incoming and outcoming calls.