Multicast Models

ASM Model

In the any-source multicast (ASM) model, any sender can act as a multicast source and send information to a multicast group address. Receivers can receive the information sent to this group after joining the group and can join and leave the group any time. Receivers do not know the multicast source location before they join a multicast group.

SFM Model

From the sender's point of view, the source-filtered multicast (SFM) model works the same as the ASM model. That is, any sender can act as a multicast source and send information to a multicast group address.

Compared with the ASM model, the SFM model extends the following function: The upper layer software checks the source addresses of received multicast packets, permitting or denying packets of multicast sources as configured.

Compared with ASM, SFM adds multicast source filtering policies. The basic principles and configurations of ASM and SFM are the same. In this document, information about ASM also applies to SFM.

SSM Model

In real-world situations, users may not require all data sent by multicast sources. The source-specific multicast (SSM) model allows users to specify multicast data sources.

Compared with receivers in the ASM model, receivers in the SSM model know the multicast source location before they join a multicast group. The SSM model uses a different address scope from the ASM model and sets up a dedicated forwarding path between a source and receivers.