Ali

PIM dense-mode by default automatically floods traffic throughout the network and if there are no interested parties routers prune themselves so they do not receive packets any more. It is primarily used on a LAN as it is quite inefficient in terms of bandwidth but even on the LAN PIM sparse-mode has become more the norm.

PIM sparse-mode does not automatically flood multicast traffic, rather it is up to routers to request the traffic if they have interested receivers. It is definitely the one to use across the WAN and as mentioned above often on the LAN as well.

PIM sparse-mode is more complicated to configure although not by much to be honest.

PIM sparse-dense mode allows the router to use dense mode in certain situations because sparse-mode cannot be used.

4 & 5 are both relevant to PIM sparse-mode.

4 configures the router to be an RP (Rendevous Point) and allows the router to send RP-Announce messages using Auto-RP.

5 configures the router to be a mapping agent ie a router that maps multicast groups to RP's and allows the router to send RP-Discovery messages using Auto-RP.

HTH

Jon