Managing Subscriber Overcommitment
The reverse-oif-mapping statement enables the routing device to identify a subscriber VLAN or interface based on an IGMP or MLD join or leave request it receives over the multicast VLAN. Once the subscriber VLAN is identified, the routing device immediately adjusts the quality of service (in this case, the bandwidth) on that VLAN based on the addition or removal of a subscriber.
Hierarchical bandwidth adjustment is performed for all subscriber interfaces with reverse OIF mapping enabled on the specified multicast interface. Hierarchical bandwidth adjustment enables you to apply traffic shaping parameters to an individual subscriber interface rather than to all interfaces configured on the port. This can prevent bandwidth contention at the interface from causing degradation of the subscriber’s voice, data, or video services. You can disable hierarchical bandwidth adjustment by including the no-qos-adjust statement.
To introduce a delay to the QoS update, use the subscriber-leave-timer statement. This statement defines a time delay (between 1 and 30 seconds) that the routing device waits before updating the QoS for the remaining subscriber interfaces after receiving an IGMP or MLD leave request. You might use this delay to decrease how often the routing device adjusts the overall QoS bandwidth on the VLAN when a subscriber sends rapid leave and join messages (for example, when changing channels in an IPTV network).
The routing device uses IGMP and MLD join or leave reports to obtain the subscriber VLAN information. This means that the connecting equipment (for example, the DSLAM) must forward all IGMP and MLD reports to the routing device in order for this feature to function properly. Using report suppression or an IGMP proxy can result in reverse OIF mapping not working properly.
You can include this statement at the following hierarchy levels:
- [edit logical-systems logical-system-name routing-instances routing-instance-name routing-options multicast]
- [edit logical-systems logical-system-name routing-options multicast]
- [edit routing-instances routing-instance-name routing-options multicast]
- [edit routing-options multicast]
