3com 5500-ei pwr Instrução De Instalação

 

3 

corresponding interface from the outgoing interface list in the (S, G) entry and stop forwarding 

subsequent packets addressed to that multicast group down to this node.  

 

z 

An (S, G) entry contains the multicast source address S, multicast group address G, outgoing 

interface list, and incoming interface. 

z 

For a given multicast stream, the interface that receives the multicast stream is referred to as 

“upstream”, and the interfaces that forward the multicast stream are referred to as “downstream”.  

 

A prune process is first initiated by a leaf router. As shown in 

, a router without any receiver 

attached to it (the router connected with Host A, for example) sends a prune message, and this prune 

process goes on until only necessary branches are left in the PIM-DM domain. These branches 

constitute the SPT.  

Figure 4-1 SPT building 

 

 

The “flood and prune” process takes place periodically. A pruned state timeout mechanism is provided. 

A pruned branch restarts multicast forwarding when the pruned state times out and then is pruned again 

when it no longer has any multicast receiver.  

 

Pruning has a similar implementation in PIM-SM.  

 

When a host attached to a pruned node joins a multicast group, to reduce the join latency, PIM-DM uses 

a graft mechanism to resume data forwarding to that branch. The process is as follows: