A conferencing system includes a plurality of ports for network connection to endpoint devices of participants to a conference session. A mixer receives input audio streams from the endpoint devices and then outputs a mixed audio stream back to the endpoint devices. A processor runs a program that automatically downgrades one or more of the participants to the conference session from a full-duplex communication mode to a half-duplex communication mode in response to an event affecting allocation of conferencing resources, the conferencing resources including the ports.