Extreme Networks devices support version 2 of the PIM protocol as described in RFC 4601 and draft-ietf-pim-sm-v2-new-09.
The PIM specifications define several modes or methods by which a PIM router can build the distribution tree. Extreme Networks devices support sparse mode (PIM-SM), dense mode (PIM-DM) and source-specific multicast (PIM-SSM).
PIM-SM uses only those routers that need to be included in forwarding multicast data. PIM-SM uses a host-initiated process to build and maintain the multicast distribution tree. Sparse mode routers use bandwidth more efficiently than other modes, but can require more processing time when working with large numbers of streams.
PIM-SSM is a subset of the PIM-SM protocol. PIM-SSM is disabled by default and must be explicitly enabled. PIM-SSM builds trees that are rooted in just one source, offering a more secure and scalable model for a limited amount of applications such as broadcasting of content. PIM-SSM is not independent of PIM-SM. PIM-SM must be enabled on all interfaces that use PIM-SSM. In PIM-SSM, an IP datagram is transmitted by a source S to an SSM destination address G, and receivers can receive this datagram by subscribing to channel (S,G). The destination address range for PIM SSM is 232.0.0.0/8 for IPv4 and ff3x:0000/32 where (x = 4,5,8, or E) for IPv6.
PIM-SSM does not require an RP candidate or BSR candidate. In a mixed PIM-SM and PIM-SSM configuration, the RP candidate and BSR candidate need to be configured for the PIM-SM group address range only. Enable IGMP on all PIM-SSM interfaces and enable IGMP querying on the PIM-SSM receiver interface. PIM-SSM requires IGMPv3 and MLDv2 at the edge of the network to process the source-specific IGMP and MLD joins.
PIM-DM creates a source-based distribution tree with minimal configuration for networks containing receivers for most PIM enabled network interfaces for any given multicast data stream.
Key features of PIM-SM are the following:
Key features of PIM-SSM are the following:
Key features of PIM-DM are the following:
Extreme Networks PIM-SM-enabled devices use the following message types:
PIM-SM adopts RPF technology in the join/prune process. When a multicast packet arrives, the router first judges the correctness of the arriving interfaces:
A router directly connected to the hosts is often referred to as a leaf router or DR. The leaf router is responsible for sending the prune messages to the RP, informing it to stop sending multicast packets associated with a specific multicast group. When the RP receives the prune message, it will no longer forward the multicast traffic out the interface on which it received the prune message.
The PIM-SSM implementation is a subset of PIM-SM protocol. PIM-SM and PIM-SSM can coexist on a single router and are both implemented using the PIM-SM protocol.
Extreme Networks PIM-SSM enabled devices use the following PIM-SM message types:
The PIM-DM-enabled devices use the following message types: