With the rapid growth of variety in networked multimedia applications over the Internet, active gateways between senders and receivers become more and more desirable. However, there are at least two major concerns to use the active network concept for multimedia communication at a gateway: (1) support of bounded end-to-end configuration delays when a gateway is dynamically configured with QoS services during media transmission, to maintain minimum QoS degradation (e.g. Jitters) and (2) support of bounded reconfiguration delays for fault tolerance handling when a gateway goes down and a new gateway needs to be reconfigured. We have designed, implemented and experimented with a QoS-aware active gateway architecture which addresses the two above described concerns. Our experiments and results show that an active gateway with flexible QoS services can be configured in an efficient manner and QoS guarantees can be preserved during the configuration/reconfiguration time if no additional security services such as authentication have to be performed at each reconfiguration request. In case of authentication our results show that the QoS will be degraded over a period of time and upgraded once the reconfiguration process is finished.