A system for admission and flow control is disclosed. In some embodiments, the system includes a switch for routing network traffic, having multiple classes of service (CoSs), from multiple ingress ports to one or more of multiple egress ports. The system also includes multiple ingress-level class of service queues (InCoS-Qs) and one or more egress-level class of service queues (EgCoS-Qs), each InCoS-Q and EgCoS-Q corresponding to one of CoSs. The switch is configured to detect congestion in a particular EgCoS-Q, corresponding to a particular CoS, the particular EgCoS-Q being associated with a particular host; identify an InCoS-Q corresponding to that particular CoS, and associated with that particular host; and block that InCoS-Q, while allowing routing of the network traffic from one or more InCoS-Qs corresponding to that particular CoS, the one or more InCoS-Qs corresponding to one or more other hosts.