QoS considerations

In per-sap replication mode (which is applicable only to IPoE subscribers), multicast traffic is forwarded through the SAP queue which is outside of the subscriber’s queues and therefore not accounted in subscriber aggregate rate limit. HQoS Adjust is used to remedy this situation.

If the SAP queue is removed from the static SAP in IPoE 1:1 model (with profiled-only-traffic command), multicast traffic flows through internal queues which cannot be tied into a port-scheduler as part of HQoS. Consequently, the port-scheduler max-rate as defined in the port scheduler policy is used only to rate limit unicast traffic. In other words, the max-rate value in the port scheduler policy must be lowered for the amount of anticipated multicast traffic that flows through the port where the port scheduler policy is applied.

A similar logic applies to the per-sap replication mode on dynamic SAPs (MSAPs) even if the SAP queue is not removed. Although the multicast traffic is flowing through the SAP queue in this case, the SAP QoS policy on MSAP cannot be changed from the default one. The default QoS policy on a SAP contains a single queue that is not parented by the port-scheduler.

Those restrictions do not apply to static SAPs where the SAP QoS policy can be customized and its queues consequently tied to the port-scheduler.