To provide multicasting services, you need a host membership protocol and a multicast routing protocol. Hosts subscribe to multicast services using a host membership protocol. The Internet Group Management Protocol (IGMP) is an example of an IPv4 host membership protocol.
A multicast routing protocol optimizes the routing of multicast information to avoid loops and restrict multicast traffic to networks that use host membership. Examples of multicast routing protocols include Protocol Independent Multicast–Sparse Mode (PIM–SM) and Protocol Independent Multicast–Source Specific Multicast (PIM–SSM).