Shared-queue QoS policies can be implemented to facilitate queue consumption on the router. It is especially useful when VPLS, IES, and VPRN services are scaled to very high numbers. Instead of allocating multiple hardware queues for each unicast queue defined in a SAP ingress QoS policy, SAPs with the shared-queuing feature enabled only allocate one hardware queue for each SAP ingress QoS policy unicast queue.
However, as a trade-off, the total amount of traffic throughput at the ingress of the node is reduced because any ingress packet serviced by a shared-queuing SAP is recirculated for further processing. Shared-queuing can add latency. Network planners should consider these restrictions while trying to scale services on the router.