The Internet Protocol and other network addressing systems recognize five main addressing methods:
Unicast addressing uses a one-to-one association between a sender and destination: each destination address uniquely identifies a single receiver endpoint.
Broadcast uses a one-to-all association; a single datagram from one sender is routed to all of the possibly multiple endpoints associated with the broadcast address. The network automatically replicates datagrams as needed to reach all the recipients within the scope of the broadcast, which is generally an entire network subnet.
Multicast addressing uses a one-to-many-of-many or many-to-many-of-many association; datagrams are routed simultaneously in a single transmission to many recipients. It differs from broadcast in that the destination address designates a subset, not necessarily all, of the accessible nodes.
Anycast addressing is a one-to-one-of-many association where datagrams are routed to any single member of a group of potential receivers that are all identified by the same destination address. The routing algorithm selects the single receiver from the group based on which is the nearest according to some distance measure.
Geocast refers to the delivery of information to a group of destinations in a network identified by their geographical locations. It is a specialized form of multicast addressing used by some routing protocols for mobile ad hoc networks.