protocol independent multicast (Routing) (PIM)

Protocol Independent Multicast(PIM) is a multicast technique that works independently of the routing protocol. In this technique, additional information is provided to the routing protocols for multicast operation. The PIM protocol, which is functionally similar to the Distance Vector Multicast Routing Protocol( DVMRP), does not use a unicast routing protocol.

The PIM protocol provides two modes. Which of the two modes is used depends on the available bandwidth and the distribution of end stations in the network. There is the Dense mode (PIM- DM) with flooding algorithm and the Sparse mode (PIM- SM) based on rendezvous points. In Dense mode, the multicast source sends its content to each destination until it explicitly unsubscribes from the group. This mode is suitable for multicast networks where the ratio between subscribers and network strands is balanced. Sparse mode is based on Core Based Tree( CBT) and uses a single data distribution tree for each group, with the core router as the root. In sparse mode, the receiver must make a request to its next multicast router, or directly to the actual source, to join the group.

Protocol Independent Multicast is an IETF specification and described under RFC 2362.