Video conference system and method using multicast and unicast transmissions

A computer-readable storage device comprising operational instructions that, when executed by a processor, cause the processor to:

• send a registration message to a call control agent device via a first unicast transmission;
• receive a set up message in response to the registration message from the call control agent device via a second unicast transmission, the set up message including an identification of a multicast control group and an identification of a first multicast group to provide incoming video conference data;
• join the multicast control group;
• join the first multicast group to receive incoming video conference data;
• receive a control message via the multicast control group;
• and
• change from receiving the incoming video conference data via the first multicast group to receiving the incoming video conference data via a second multicast group when content of the message indicates that the processor is to receive the incoming video conference data via the second multicast group.

A first video conference terminal, comprising:

• a processor;
• and
• a memory including operational instructions that, when executed by the processor, cause the processor to:
• receive, from a call control agent, a first call control message identifying the first video conference terminal as an active talker and identifying a second video conference terminal as a previous talker;
• send first outgoing video conference data from the first video conference terminal to the second video conference terminal and at least a third video conference terminal that are joined to a first multicast group associated with the active talker;
• and
• receive incoming video conference data at the first video conference terminal via a second multicast group associated with the previous talker.