An impairment unit, method, and machine readable storage media for emulating network impairments. A first network interface may receive network traffic including a plurality of received packets. A classifier may determine an impairment class of each received packet based on test information contained within a payload portion of each received packet, the impairment class of each received packet being one of a plurality of impairment classes, each impairment class uniquely associated with a corresponding one of a plurality of impairment profiles. An impairment engine may impair each of the plurality of impairment classes in accordance with the corresponding impairment profile to provide impaired network traffic. A second network interface may transmit the impaired network traffic to the network.