A method and apparatus for adaptively enforcing Quality of Service (QoS) policies for one or more flows of packets in a packet-switched network based on network feedback information. In one aspect, packets of a first group of flows are assigned to a first service level. Then-current interface congestion information for network traffic that is mapped to the first service level and that is passing through an interface of a network device in the network is received. Based on the then-current interface congestion information one or more flows from the first group of flows are selected. Packets from the one or more flows are then assigned to a second service level.