Protocol Independent Multicast-Sparse Mode

Table 1. Protocol Independent Multicast - Sparse Mode product support

Feature

Product

Release introduced

Protocol Independent Multicast-Sparse Mode (PIM-SM) for IPv4

5320 Series

Fabric Engine 8.6

5420 Series

VOSS 8.4

5520 Series

VOSS 8.2.5

PIM Infinite Threshold for IPv4 and IPv6

5320 Series

Fabric Engine 8.6

5420 Series

VOSS 8.5

5520 Series

VOSS 8.5

Note

Note

PIM is supported in Global Routing Table (GRT) only.

PIM-SM, as defined in RFC2362, supports multicast groups spread out across large areas of a company or the Internet. PIM-SM sends multicast traffic only to routers that specifically join a multicast group. This technique reduces traffic flow over WAN links and overhead costs for processing unwanted multicast packets.

Dense-mode protocols use a flood-and-prune technique, which is efficient with densely-populated receivers. However, for sparsely populated networks, PIM-SM is more efficient because it sends multicast traffic only to those routers that belong to a specific multicast group and that choose to receive the traffic.

PIM-SM is independent of a specific unicast routing protocol, but it does require the presence of a unicast routing protocol, such as Routing Information Protocol (RIP) or Open Shortest Path First (OSPF). PIM-SM uses the information from the unicast routing table to create and maintain multicast trees that enable PIM-enabled routers to communicate.

Typically, a PIM-SM network consists of several multipoint data streams, each targeted to a small number of LANs in the internetwork. For example, customers whose networks consist of multiple hosts on different LANs can use PIM-SM to simultaneously access a video data stream, such as video conferencing, on a different subnet.

Important

Important

In some cases, PIM stream initialization can take several seconds.

Hosts

A host is a source, a receiver, or both:

PIM-SM domain

PIM-SM operates in a domain of contiguous routers on which PIM-SM is enabled.

Each PIM-SM domain requires the following routers:

Although a PIM-SM domain can use only one active RP router and one active BSR, you can configure additional routers as a candidate RP (C-RP) router and as a candidate BSR (C-BSR). Candidate routers provide backup protection in case the primary RP router or BSR fails.

As a redundancy option, you can configure several RPs for the same group in a PIM domain. As a load sharing option, you can have several RPs in a PIM-SM domain map to different groups. The switch devices use the hash function defined in the PIM-SM standard to elect the active RP.

Designated router

The designated router (DR), the router with the highest IP address on a LAN, performs the following tasks:

Important

Important

The DR is not a required configuration. Switches act automatically as the DR for directly attached sources and receivers.