Reservation proxy function supporting filtering of multicast traffic in packet-based communication systems

In a communication system organized into a plurality of communication zones having respective zone controllers, one or more of the zone controllers defining participating zone controllers having joined a multicast group address to participate in a call and having indicated, to one or more network devices, a desire to receive packets from certain specified senders during the call, a method comprising:

• determining that a new zone should be added to the call;
• redefining the specified senders to include a new zone controller associated with the new zone;
• joining, by the new zone controller, the multicast group address;
• sending, by the new zone controller to the one or more network devices, one or more messages defining the participating zone controllers as eligible senders from which packets addressed to the multicast group address are eligible to be received during the call;
• and
• exchanging control messages between the new zone controller and the eligible senders to establish a reservation of communication resources for the new zone on behalf of participating hosts in the new zone.