Juniper Networks® Field Guide and Reference

PIM

Protocol-Independent Multicast (PIM) is used to efficiently route to multicast groups that might span wide-area and interdomain internetworks. It is referred to as “protocol independent” because it is not dependent on any particular unicast routing protocol. The software supports both sparse mode and dense mode. In sparse mode, routers must join and leave multicast groups explicitly. Upstream routers do not forward multicast traffic to this router unless this router has sent an explicit request (using a join message) to receive multicast traffic. When a host joins a multicast group, its first-hop router sends a join message upstream toward the rendezvous point (RP) for the group. The RP serves as the root of the shared multicast delivery ...