Many real-time, multimedia applications (e.g., teleconferencing) have been successful deployed over the Internet and its overlayed multicast backbone network (MBONE). However poor, unpredictable transfer performance of the continuous media in Internet is common and inevitable due to the intrinsic "best-effort" transport techniques used. Before the full-blown ATM networks or any other networks with QoS offerings are in place, Ethernets are still the most popular networks in today's office environments. We investigate how application-level traffic shaping (spacing) can help to reduce the possibly drastic performance degradation of real-time multimedia conferencing applications on a heavily-loaded Ethernet. An experimental testbed is constructed and all the application software is implemented in our laboratory. Performance results measured from the testbed are presented to provide insights of how the performance degradations occur and to illustrate how a real-time application can lessen the situation.