PIM

Introduction

Protocol-Independent Multicast (PIM) can forward multicast packets with a unicast protocol.

PIM efficiently routes multicast traffic for groups that span wide area (and inter-domain) networks.

It works with all existing unicast routing protocols.

PIM in Gaia Embedded supports these modes:

  • Dense Mode (PIM DM)

  • Sparse Mode (PIM SM)

  • Source-Specific Multicast Mode(PIM SSM)

Important - The implementation does not support enabling both Dense Mode and Sparse Mode, or either mode of PIM and DVMRP on the same appliance.

Note - You can run PIM over a route-based VPN by enabling PIM on an unnumbered Virtual Tunnel Interface (VTI).

Important - In a cluster, you must configure the routing settings separately on each Quantum Spark Cluster Member.

PIM Dense Mode (DM)

This mode is most useful when:

  • Senders and receivers are in close proximity to one another.

  • There are few senders and many receivers.

  • The volume of multicast traffic is high.

  • The stream of multicast traffic is constant.

PIM Sparse Mode (SM)

This mode is most useful when:

  • There are few receivers in a group.

  • Senders and receivers are separated by WAN links.

  • The type of traffic is intermittent.

PIM Source-Specific Multicast (SSM) Mode

This mode is most useful when:

  • Most multicast traffic is from well-known sources.

  • It is desirable to avoid the overhead of shared tree and rendezvous point processing associated with sparse mode.

SSM is a version of PIM Sparse Mode. It is used in conjunction with IGMP v3 to request or block multicast traffic from specific sources. For example, when a host requests traffic for a multicast group from a specific source, SSM sends PIM join/prune messages towards the source.

The multicast group range 232.0.0.0/8 is reserved for SSM. When SSM is enabled, Sparse Mode accepts only IGMP v3 reports for groups that fall within this range. Sparse Mode ignores IGMP v1 and IGMP v2 reports in this range.

In addition, only shortest-path-tree (SPT) join/prune messages for these groups are accepted from neighboring routers. All other multicast groups are processed as in native Sparse Mode.

SSM does not need a Rendezvous Point (RP). The presence of an RP for any of the SSM groups does not have any influence on the processing of join/prune messages.