|
Feature |
Product |
Release introduced |
|---|---|---|
|
For configuration details, see VOSS User Guide. |
||
|
Protocol Independent Multicast-Sparse Mode (PIM-SM) for IPv4 |
5520 Series |
VOSS 8.2.5 |
|
VSP 4450 Series |
VOSS 4.1 |
|
|
VSP 4900 Series |
VOSS 8.1 |
|
|
VSP 7200 Series |
VOSS 4.2.1 |
|
|
VSP 7400 Series |
VOSS 8.0 |
|
|
VSP 8200 Series |
VOSS 4.0.1 |
|
|
VSP 8400 Series |
VOSS 4.2 |
|
|
VSP 8600 Series |
VSP 8600 4.5 |
|
|
XA1400 Series |
Not Supported |
|
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
In some cases, PIM stream initialization can take several seconds.
A host is a source, a receiver, or both:
A source, also known as a sender, sends multicast data to a multicast group.
A receiver receives multicast data from one or several sources that sends data to a multicast group.
PIM-SM operates in a domain of contiguous routers on which PIM-SM is enabled.
Each PIM-SM domain requires the following routers:
designated router (DR)
rendezvous point (RP) router
bootstrap router (BSR)
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.
The designated router (DR), the router with the highest IP address on a LAN, performs the following tasks:
sends register messages to the RP router on behalf of directly connected sources
sends join and prune messages to the RP router on behalf of directly connected receivers
maintains information about the status of the active RP router for local sources in each multicast group
Important
The DR is not a required configuration. Switches act automatically as the DR for directly attached sources and receivers.