Remote process control and supervision applications developed over the Internet require special communication models and techniques, which can guarantee the real-time and safety restrictions inherent to automation systems. This paper presents a communication model based on data flow analysis and bandwidth reservation that offers a good control over the transmission time of critical data. As part of the model, an analytical method is proposed that allows apriory evaluation of the required minimum bandwidth necessary to assure the fulfillment of real-time transmission restrictions. The model is based on the QoS facilities offered by the IPv6 protocol.