TP-Link JetStream T2700G-28TQ User Manual page 263

RPT Building
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As shown in Figure 11-17, the establishing process of RPT is illustrated below:
(1) When a receiver joins a multicast group G, it informs the directly connected DR with IGMP
message;
(2) After receiving the IGMP message from multicast group G, the DR sends PIM join message
toward the corresponding root, also known as the RP;
(3) The join message travels router-by-router toward the root, constructing a branch of the RPT
as it goes. These routers generate (*, G) entries in their forwarding tables with * representing
any multicast source. The RPT works with RP as the root node, and DR as the branch node.
When multicast data for multicast group G is sent to RP, it will travels along the constructed RPT
to DR and finally arrives at the receivers.
When a receiver is no longer interested in the multicast group data, its directly connected DR will
send prune message up the RPT toward the group's corresponding RP; after the upstream node
receives this prune message, it will delete the link to the downstream node in its interface list and
Figure 11-16 The Locations of C-RP, C-BSR and BSR
Figure 11-17 RPT Topology in PIM SM
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