Overview PIM-DM

PIM-DM (Protocol Independent Multicast-Dense Mode) is applicable when the group members are relatively concentrated and the range is small, or the network bandwidth resource is sufficient.

PIM-DM does not depend on the specified unicast route protocol for the RPF check.

PIM-DM adopts the “Push” to transmit the multicast packets. When the multicast source starts to send the multicast packets, suppose that all subnets in the multicast domain have the multicast receivers, so the multicast packets are pushed to all nodes in the network. PIM-DM forwards and prunes the multicast without the receiver. When the node of the pruned multicast forwarding branch node has the receiver of the multicast source, PIM-DM uses the graft mechanism to actively restore the forwarding of the multicast data.

PIM-DM uses the status refresh mechanism to refresh the downstream status regularly so that the pruned branch does not time out.