Multicasting system

A multicast system includes a source device and a plurality of receiver devices connected by switches that are also coupled to a switch controller. The switch controller receives source device information for the source device from its connected first switch, and receives receiver device information for each of the receiver devices from their respective connected second switches. The switch controller uses the source device information and receiver device information to construct a multicast tree that includes switches capable of transmitting multicast communications from the source device to each of the receiver devices. The switch controller then programs at least some of the switches so that a multicast data communication from the source device is segment routed to a third switch, and replicated by the third switch to produce replicated multicast data communications that are each segment routed to at least some of the receiver devices through their respective second switches.