The AN is configured as IGMP/MLD Proxy node and is participating in downstream multicast replication.
For IPv4, IGMP messages from multiple sources (subscribers hosts) for the same multicast group are consolidated in the AN into a single IGMP messages. This single IGMP message has the source IP address of the AN.
For IPv6, MLD messages from multiple sources (subscribers hosts) for the same multicast group are consolidated in the AN into a single MLD messages. This single MLD message has the link-local IP address of the AN.
From the BNG perspective this deployment model has the following characteristics:
Subscriber IGMP/MLD states are maintained in the AN.
IGMP Joins are accepted from the source IP address that is different from any of the subscriber’s IP addresses already existing in the BNG. This is controlled by an IGMP filter on a per group-interface level assuming that the IGMP processing for subscriber hosts is disabled with the no sub-hosts-only command under the router/service vprn>igmp>group-interface CLI hierarchy. In this case all IGMP messages that cannot be related to existing hosts are treated in the context of the SAP while IGMP messages from the existing hosts are treated in the context of the subscriber hosts.
MLD Joins are only accepted if the link-local address matches the subscriber’ link local address. To allow processing of foreign link-local address such as the AN link local address, the MLD processing for subscriber hosts should be disabled with the no sub-hosts-only command under the router/service vprn>mld>group-interface CLI hierarchy. In this case all MLD messages that cannot be related to existing hosts are treated in the context of the SAP while MLD messages from the existing hosts are treated in the context of the subscriber hosts.
IGMP/MLD statistics can be displayed per group-interface.
Multicast traffic for all subscribers on this SAP is forwarded through the egress SAP queue.
A single copy of any multicast stream is generated per SAP.
The AN receives a single multicast stream. Based on the IGMP/MLD proxy information, the AN replicates the mcast stream to the appropriate subscribers.
Traffic statistics are maintained per SAP queue.
HQoS Adjustment is not useful because the per host/subscriber IGMP/MLD granularity is lost. IGMP/MLD states are aggregated per AN.
Traffic can be explicitly classified into a specific SAP queues by a QoS policy applied under the SAP.
Multicast streams have multicast destination MAC.
In the following example, IGMPs from the source IP address <ip> is accepted even though there is no subscriber-host with that IP addresses present in the system. An IGMP state is created under the SAP context (service per vlan, or N:1 model) for the group pref-definition. All other IGMP messages originated from non-subscriber hosts is rejected. IGMP messages for subscriber hosts are processed according to the IGMP policy applied to each subscriber host.
configure
service vprn <id>
igmp
group-interface <ip-int-name>
import <policy-name>
configure
router
policy-options
begin
prefix-list <pref-name>
prefix <pref-definition>
policy-statement proxy-policy
entry 1
from
group-address <pref-name>
source-address <ip>
protocol igmp
exit
action accept
exit
exit
default-action reject
This functionality (accepting IGMP from non-subscriber hosts) can be disabled with the following flag.
configure
service vprn <id>
igmp
group-interface <ip-int-name>
sub-host-only
In this case, only per host IGMP processing is allowed.
In the following example, MLDs with foreign link-local-address is accepted even though there is no subscriber-host with that link local addresses present in the system. An MLD state is created under the SAP context (service per vlan, or N:1 model) for the group pref-definition. All other MLD messages originated from non-subscriber hosts are rejected. MLD messages for subscriber hosts are processed according to the IGMP policy applied to each subscriber host.
configure
service vprn <id>
mld
group-interface <ip-int-name>
import <policy-name>
configure
router
policy-options
begin
prefix-list <pref-name>
prefix <pref-definition>
policy-statement proxy-policy
entry 1
from
group-address <pref-name>
source-address <ip>
protocol igmp
exit
action accept
exit
exit
default-action reject
This functionality (accepting MLD from non-subscriber hosts) can be disabled with the following flag.
configure
service vprn <id>
mld
group-interface <ip-int-name>
sub-host-only
In this case, only per host MLD processing is allowed.
This model is shown in Figure: N:1 model - AN in proxy mode.
