The AN is IGMP/MLD aware and is participating in multicast replication. From the BNG perspective this deployment model has the following characteristics:
IGMP/MLD states are kept per hosts and SAPs. Each host can be registered to more than one group.
IGMP/MLD Joins are accepted only from the active subscriber hosts as dictated by antispoofing.
IGMP/MLD statistics are displayed per host, per group or per subscriber.
Multicast traffic for all subscribers on this SAP is forwarded through the egress SAP queues.
A single copy of any multicast stream is generated per SAP. This can be viewed as the replication per unique multicast group per SAP, instead of the replication per host or subscriber. In other words, the number of multicast streams on this SAP is equal to the number of unique groups across all hosts and subscribers on this SAP.
The AN receives a single multicast stream and based on its own (AN) IGMP/MLD snooping information, it replicates the mcast stream to the appropriate subscribers.
Traffic statistics are kept per the SAP queue. Consequently multicast traffic stats are shown on a per SAP basis (aggregate of all subscribers on this SAP).
Traffic cannot be explicitly classified (forwarding classes and queue mappings) inside of the subscriber queues.
Redirection to the common multicast VLAN is supported.
Multicast streams have multicast destination MAC.
IGMP Joins are accepted (src IP address) only for the sub hosts that are already created in the system. IGMP Joins coming from the hosts that are nonexistent in the system are rejected, unless this functionality is explicitly enabled by the sub-hosts-only command under the IGMP group-int CLI hierarchy level.
MLD uses link-local as source address, which makes it difficult to associate with the originating host. MLD (S,G) are always first associated with a IPv6 WAN host, if available. If this WAN host terminate its IPv6 session (by lease expiry, session terminate, and so on), the (S,G) is then associated with any remaining WAN host. Only when there are no more WAN hosts available, is the (S,G) associated with the PD host, if any.
MLD join are only accepted if it matches the subscriber host link local address. MLD Joins coming from the hosts that are nonexistent in the system is rejected, unless this functionality is explicitly enabled by the sub-hosts-only command under the MLD group-int CLI hierarchy level.
This model is shown in Figure: N:1 model - AN in IGMP snooping mode.
Figure: N:1 model - AN in IGMP snooping mode