Abstract. This paper presents a system, called mTunnel, for application level tunneling of multicast trac in a lightweight manner, where the end-user is responsible for deciding which MBone-sessions and multicast groups to tunnel. mTunnel is primarily designed for easy deployment and easy-to-manage tunneling. Therefore it runs as an user application and does not need access to restricted system resources. Information about currently tunneled sessions and control of mTunnel is provided through a Web-interface. To allow the user to easily start tunneling of announced MBone-sessions, mTunnel listens for announcements and presents this information through the Web-interface. To save bandwidth, tunneled streams can be translated in four ways: audio streams can be recoded to an encoding that requires lower bandwidth, several audio streams can be mixed together, streams can be switched based on activity in another stream and streams can be scaled by dropping a certain percent of the trac.