Which method is used to direct communications to a group of computers that subscribe to the transmission?

Multicast is used to allow computers to opt into a transmission. Examples of uses for multicast are video, routing protocols, and imaging of computers to name a few. A unicast address is a single valid IP address for direct communications purposes between two hosts. A broadcast will forward a message to all computers in the same subnet. A multicast address is a single address that is selectively sent to a multicast group of hosts. Anycast is a way of allowing the same IP address on multiple machines in different geographical areas. The routing protocol is used to advertise in routing tables the closest IP by the use of metrics.