PIM Sparse Mode Operation

C.

PIM (Protocol Independent Multicast) is a multicast routing protocol used to efficiently distribute multicast traffic in a network. PIM has two modes: Sparse mode and Dense mode.

PIM sparse mode operates on a shared tree mechanism. In this mode, multicast traffic is initially sent to the RP (Rendezvous Point) router, which is responsible for tracking the source of the multicast traffic and forwarding it down the shared tree to the receivers. The RP can be configured statically or dynamically, and it is responsible for maintaining the distribution tree.

Option A is accurate since if there are multiple multicast groups and sources in the network, multicast traffic must always flow through the RP and down the shared tree to get to the receivers. This can cause a bottleneck at the RP and lead to a delay in traffic delivery.

Option B is incorrect since in PIM sparse mode, traffic is not switched to a shortest path tree when more than one receiver is present.

Option C is also incorrect since PIM sparse mode can have backup RPs that can take over if the primary RP fails. In this case, the new sources that begin sending will be discovered by the other PIM routers in the network.

Option D is also incorrect since even if the RP fails and there is no backup RP, multicast traffic will still continue to flow in the network. However, new sources will not be able to join the multicast group.

In conclusion, option A accurately describes how PIM sparse mode operates.