A multicast is a single data stream sent from one source to a group of recipients. Examples might be a stock ticker or live video feed. Figure 7-3 shows an example multicast topology, as contrasted to unicast and broadcast.
Figure 7-1. Multicast Topology
In contrast, a unicast is traffic from one source to one destination (see Figure 7-2).
Figure 7-2. Unicast Topology
A broadcast is traffic from one source to all destinations (see Figure 7-3). Broadcasts are not routed!
Figure 7-3. Broadcasting
Some features of multicast traffic ...