Abstract: The present invention relates to a switching unit with a scalable and QoS aware flow control. The actual schedule rate of an egress queue, wherein the outgoing traffic belonging to a particular class of service is backlogged, is measured and compared to its expected schedule rate. If the egress queue is scheduled below expectation, then the bandwidth of every virtual ingress-to-egress pipe connecting an ingress queue, wherein the incoming traffic belonging to the same class of service is backlogged before transmission through the switch core fabric, to that egress queue is increased, thereby feeding that egress queue with more data units.