3com 5500-ei pwr Instrução De Instalação

 

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Figure 4-5 Building an RPT in PIM-SM RPT building  

 

 

 

As shown in 

, the process of building an RPT is as follows:   

1)  When a receiver joins a multicast group G, it uses an IGMP message to inform the directly 

connected DR. 

2)  Upon getting the receiver information, the DR sends a join message, which is hop by hop 

forwarded to the RP corresponding 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 * means any multicast source.  The RP is the 

root, while 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 a multicast group G, the 

directly connected DR sends a prune message, which goes hop by hop along the RPT to the RP. Upon 

receiving the prune message, the upstream node deletes its link with this downstream node from the 

outgoing interface list and checks whether it itself has receivers for that multicast group. If not, the router 

continues to forward the prune message to its upstream router.  

The purpose of multicast source registration is to inform the RP about the existence of the multicast 

source.