摘要：Multicast IP network services offer new opportunities to provide value-added applications that involve many-tomany transmission such as conferencing or network gaming, or one-to-many transmission such as multimedia events, tickertape feeds, and file transfer, where the many could be thousands or even conceivably millions. Multicast IP services use a different kind of IP address, called Class D. In contrast to individual host addresses (Classes A–C), which include a host and a network component and usually are semipermanent, Class D multicast addresses may by design be used only for a particular session, or can be semipermanent, as multicast groups may be set up and torn down relatively quickly, on the order of seconds. The IP address structure is shown in Figure 1.
