To transmit a single message to a select group of recipients. A simple example of multicasting is sending an e-mail
message to a mailing list
also use multicasting, but require more robust protocols and networks.
Standards are being developed to support multicasting over a TCP/IP network such as the Internet. These standards, IP Multicast and Mbone, will allow users to easily join multicast groups.
Note that multicasting refers to sending a message to a select group whereas broadcasting refers to sending a message to everyone connected to a network.
The terms multicast and narrowcast are often used interchangeably, although narrowcast usually refers to the business model whereas multicast refers to the actual technology used to transmit the data.
Compare with unicast and anycast.