To stop floodwaters from entering roads, property, and tributaries, people build dams and place sandbags at appropriate physical locations. IP Multicast is the Internetworking equivalent that prevents broadcast-based applications from flooding your entire network. This Chapter introduces you to the Layers 24 protocols that Cisco routers and switches use for making upper-layer content networking applications more efficient.
IP Multicast technologies transport applications, such as live and on-demand audiovideo feeds, video conferencing, and file transfers between participants. In the past, if multiple receivers required the same content from a single source, the sender generated a copy for each receiver. Multicast enables you to send traffic from a single source to multiple receivers, without replicating the information at the source. Your network forwards the traffic only to segments that contain hosts interested in receiving the traffic. At any given point in your network, there is never more than a single flow of the content on the same link. The result is an efficient use of bandwidth for disseminating your content.
For more information on applications and protocols that benefit from IP Multicast, see Chapter 9, "Introducing Streaming Media".