Jump to content

PIM Sparse Mode

Add links
From Wikipedia, the free encyclopedia
This is an old revision of this page, as edited by Brindalv (talk | contribs) at 11:54, 4 March 2011. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Protocol Independent Multicast - Sparse-Mode (PIM-SM) is a protocol for efficiently routing Internet Protocol (IP) packets to multicast groups that may span wide-area and inter-domain internets. The protocol is named protocol-independent because it is not dependent on any particular unicast routing protocol for topology discovery, and sparse-mode because it is suitable for groups where a very low percentage of the nodes (and their routers) will subscribe to the multicast session. Unlike earlier dense-mode multicast routing protocols such as DVMRP and dense multicast routing which flooded packets across the network and then pruned off branches where there were no receivers, PIM-SM explicitly constructs a tree from each sender to the receivers in the multicast group.

Multi-cast Clients

The hosts send IGMP Join message to subscribe to a multicast group.A router receives explicit PIM Join/Prune messages from those neighboring routers that have downstream group members.

Protocol Overview

A PIM-join message must be sent towards the source of the multicast stream.But, a PIM-SM router does not know where to forward a join request, as multicast traffic will be received only after the join request is sent out by the PIM router. This problem is solved using 3 components:

  1. Rendezvous Point
  2. Source trees
  3. Shared- trees

They are explained one after the other.

Rendezvous Point

When configuring PIM-SM on a network, at least one router must be designated as a rendezvous point (RP). The RP could be configured manually, or dynamically through Cisco's Auto-RP[1] or PIMv2's Bootstrap Router (BSR) method. Regardless of which method is used, an RP performs a critical function: it establishes a common reference point from which multicast trees are grown.

Source Trees

See also

References

  1. ^ http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080094821.shtml
Retrieved from "https://en.wikipedia.org/w/index.php?title=PIM_Sparse_Mode&oldid=417068955"