HP 6125G HP 6125G & 6125G/XG Blade Switches IP Multicast Configuration - Page 119

Value Mod Description Modulo operator, which gives the remainder of an integer division RPT building Figure 40 RPT building in a PIM-SM domain As shown in Figure 40, the process of building an RPT is as follows: 1. When a receiver joins multicast group G, it uses an IGMP message to inform the directly connected DR. 2. After getting the receiver information, the DR sends a join message, which is forwarded hop by hop to the RP that corresponds to the multicast group. 3. The routers along the path from the DR to the RP form an RPT branch. Each router on this branch generates a (*, G) entry in its forwarding table. The asterisk means any multicast source. The RP is the root of the RPT, and the DRs are the leaves of the RPT. The multicast data addressed to the multicast group G flows through the RP, reaches the corresponding DR along the established RPT, and finally is delivered to the receiver. When a receiver is no longer interested in the multicast data addressed to multicast group G, the directly connected DR sends a prune message, which goes hop by hop along the RPT to the RP. After receiving the prune message, the upstream node deletes the interface that connects to this downstream node from the outgoing interface list and determines whether it has receivers for that multicast group. If not, the router continues to forward the prune message to its upstream router. Multicast source registration The purpose of multicast source registration will inform the RP about the existence of the multicast source. 108