PIM Dense

Note: This section describes the "dense" mode of PIM, described in RFC 3973. Refer to PIM Sparse for information about PIM Sparse.

PIM was introduced to simplify some of the complexity of the routing protocol at the cost of additional overhead tied with a greater replication of forwarded multicast packets. PIM builds source-routed multicast delivery trees and employs reverse path check when forwarding multicast packets.

There are two modes in which PIM operates: Dense and Sparse. The Dense Mode is suitable for densely populated multicast receivers, primarily in the LAN environment. The Sparse Mode is suitable for sparsely populated multicast receivers with the focus on WAN.

PIM uses the IP routing table instead of maintaining its own, thereby being routing protocol dependent.