With the growth of network broadband users and the next generation internet

the daily-increasing demand for multimedia-related services such as IPTV has activated the popularization and development of IP multicast technology

which has become an essential key technology of the next generation networks.Compared with unicast

the application of IP multicast technology for information distribution can substantially decrease the bandwidth requirements of the entire networks.Starting from the introduction of the various kinds of multicast technologies in IPv6 network

this article describes in details the multicast routing technology of the Protocol Independent Multicast（PIM）

which is widely used in present practical networks

with the emphasis on PIM-SM

the most widely-used in multicast routing.Then

it discusses the operational process of PIM-SM multicast routing protocol in IPv6 networks and ends with its prospects in future IPTV applications.