Configuring IP Multicast Protocols
For example, in Figure 9.1 the sender with address 207.95.5.1 is sending multicast packets to the group 229.225.0.1. If a PIM router receives any groups other than that group, the router discards the group and sends a prune message to the upstream PIM router.
In Figure 9.2, Router R5 is a leaf node with no group members in its IGMP database. Therefore, the router must be pruned from the multicast tree. R5 sends a prune message upstream to its neighbor router R4 to remove itself from the multicast delivery tree and install a prune state, as seen in Figure 9.2. Router 5 will not receive any further multicast traffic until the prune age interval expires.
When a node on the multicast delivery tree has all of its downstream branches (downstream interfaces) in the prune state, a prune message is sent upstream. In the case of R4, if both R5 and R6 are in a prune state at the same time, R4 becomes a leaf node with no downstream interfaces and sends a prune message to R1. With R4 in a prune state, the resulting multicast delivery tree would consist only of leaf nodes R2 and R3.
Video Conferencing
Server
(207.95.5.1, 229.225.0.1) (Source, Group)
229.225.0.1 | 229.225.0.1 |
| ||
Group | Group | Group | Group | Group |
Member | Member | Member | Member | Member |
...
R2 | R3 |
R4
... |
| R6 |
R5 |
|
|
| Leaf Node |
|
Leaf Node |
|
|
(No Group Members) | ... |
|
Interrmediate Node |
| |
(No Group Members) |
|
|
Group | Group | Group |
Member | Member | Member |
229.225.0.1
Figure 9.1 Transmission of multicast packets from the source to host group members
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