The present invention is concerned with Process Control systems including a client IED and a plurality of server IEDs connected to an Ethernet communication network. A protocol analyzer tool connected to the communication network captures messages directed to the client IED and assigns, from a standardized configuration representation of the PC system comprising the logical data flow definitions, a server or source IED to each captured message. A client IED independent way of diagnosing a cause of client overload problems is provided by analyzing statistically the captured messages. Such statistical approach allows identifying any operating server or source IED sending, on average, more messages than during a preceding period or more messages than calculated.