PIM modes
Dense-mode: source-rooted trees
- each source within a group has its own tree that connects it to all the receiving members of the group
- therefore, n sources within a group imply n distinct delivery trees
- more router state, lower delay from source
- direct or shortest path from the source to the receivers
Sparse-mode: shared trees
- multicast paths are built around a “core” router, which serves as a rendez-vous point between sources and destinations
- single tree between all sources and receivers of a given group
- less demand on routers and network bandwidth for the tree construction, but less efficient than source-rooted trees for multicast forwarding (but see later for optimizations)
- less router state, higher delay from source