What type of multicast traffic does PIM Sparse-Dense Mode use in the absence of a rendezvous point?

PIM Sparse-Dense Mode is designed to operate in both sparse and dense environments depending on the multicast group and the network configuration. In the absence of a rendezvous point (RP), PIM Sparse-Dense Mode defaults to using Dense Mode for multicast traffic.

When there is no RP present, the protocol will attempt to treat multicast traffic as if it were a dense environment. This means that PIM will flood multicast traffic throughout the network, similar to how PIM Dense Mode operates. The reason for this is to ensure that the multicast stream can still be delivered to receivers even when the control plane for sparse mode is not available.

In contrast, Sparse Mode is intended for networks where multicast group members are widely dispersed, minimizing unnecessary traffic and reducing network load. Without an RP, the network cannot establish a shared tree or utilize the behavior typically defined for Sparse Mode, so the system resorts to the density approach.

By leveraging Dense Mode under these circumstances, the network can maintain multicast service continuity despite the absence of traditional control mechanisms.