Multicasting offers a number of advantages for applications that need to communicate with multiple endpoints without the overhead of broadcasting. In this chapter, we defined multicasting and presented the different multicasting models. We then discussed how IP multicasting and ATM point-to-multipoint communication apply to these models. Finally, we covered how the Winsock API supports multicasting by presenting both the Winsock 1 method, which uses socket options, and the newer Winsock 2 method, which uses the WSAJoinLeaf function.