Dell PowerConnect M6348 Configuration Manual

Also see for PowerEdge M520: Manual Command reference guide Owner's manual Information update Release notes

Contents

Dell PowerConnect M6348 Configuration Manual Manual pdf 148 page image

148 MulticastPIMProtocol Independent Multicast (PIM) is a standard multicast routing protocol that provides scalableinter-domain multicast routing across the Internet, independent of the mechanisms provided by anyparticular unicast routing protocol.PIM has two types:• PIM-Dense Mode (PIM-DM)• PIM-Sparse Mode (PIM-SM)PIM-SMPIM-SM is used to efficiently route multicast traffic to multicast groups that may span wide areanetworks where bandwidth is a constraint.PIM-SM uses shared trees by default and implements source-based trees for efficiency; it assumes thatno hosts want the multicast traffic unless they specifically ask for it. It creates a shared distribution treecentered on a defined rendezvous point (RP) from which source traffic is relayed to the receivers.Senders first send the multicast data to the RP, which in turn sends the data down the shared tree to thereceivers. Shared trees centered on an RP do not necessarily provide the shortest, most optimal path. Insuch cases, PIM-SM provides a means to switch to more efficient source-specific trees. A data thresholdrate is configured to determine when to switch from shared-tree to source-tree.PIM-SM uses a Bootstrap Router (BSR), which advertises information to other multicast routers aboutthe RP. In a given network, a set of routers can be administratively enabled as candidate bootstraprouters. If it is not apparent which router should be the BSR, the candidates flood the domain withadvertisements. The router with the highest priority is elected. If all the priorities are equal, then thecandidate with the highest IP address becomes the BSR.PIM-SM is defined in RFC 4601.