It is widely known that Ethernet networks are susceptible to high-power electromagnetics (HPEM). Even with electromagnetic disturbance levels below the threshold, at which a hardware failure of components can be observed, there are impacts on the data transmission between two computers. A typical effect on the application level is a decrease of the maximum data rate between two endpoints with a higher field strength until the transmission completely breaks down. To quantify the effect of electromagnetic disturbances it is necessary to distinguish between effects which are software-related due to control algorithms and applications behaviour on higher protocol layers, and hardware-related effects caused by physical interaction between the network components and the disturbance. This paper shows the results of a new measurement method compared to classical tests using a FTP data transmission.