Network Management Strategies for the CIO
Protocol-independent multicast (PIM) is a set of four specifications that define modes of Internet multicasting to allow one-to-many and many-to-many transmission of information.
The four modes are:
- sparse mode (SM)
- dense mode (DM)
- source-specific multicast (SSM)
- bidirectional.
The most common mode in PIM is the sparse mode. It is used for transmission of data to nodes in multiple Internet domains, where it is expected that only a small proportion of the potential nodes will actually subscribe. Dense mode, in contrast to sparse mode, is used when it is expected that a large proportion of the potential nodes will subscribe to the multicast. In source-specific multicast, paths (also called trees) originate (or are rooted) at a single, defined source, whereas bidirectional PIM is not source-specific.
The term "protocol independent" means that PIM can function by making use of routing information supplied by a variety of communications protocols. In information technology, a protocol is a defined set of rules that end points in a circuit or network employ to facilitate communication.