Aiming at a practical industrial network control system, this paper makes an analysis of types of data, their traffic and directions under different working conditions, and a selection of a link of maximum traffic as a typical one. The method of passive measurement is used to obtain the packets of different protocols passing through the link. The traffic of the corresponding protocols can be calculated according to the size and arrival time of packets.
It is found from the analysis of the characteristics of main protocols that the traffics of this control system are of relatively smooth periodicity as well as abruptness, but not of obvious self-similarity or long-range dependence, which are theoretical verified. Hence, the traffic is considered a periodically abrupt process approximately on a large time scale, but not suitable for a long-range dependent or self-similar model.