Active networks provide a programmable user-network interface that supports dynamic modification of the network's behavior. Network nodes, in addition to forwarding packets, perform customized computation on the messages flowing through them. Individual packets carry executable code, or references to executable code. Active networks are changing considerably the scenery of computer networks and consequently, affect the way network management is conducted. Performance management is strongly related to quality of service (QoS) provisioning. In a heterogeneous networking environment, each node must understand the varying resource demands associated with specific network traffic. This paper describes and evaluates an approach to control the CPU utilization of malicious packets and to estimate the CPU demand for good packets in a heterogeneous active network environment. The network management systems can allocate the capacity better by anticipating varying demands and the network operators can better estimate the quality of service (QoS) that customers can expect. © 2007 IEEE.