Causes of fault
A substantial portion of all data transfer errors results from incorrect data forwarding by gateways. E.g., data duplications may occur if a network is linked to other networks via two gateways, both of which transfer the same set of data. On the other hand, data packets may be lost if a gateway does not pass on data at all, or feeds it into the wrong network. If data packets can only be transferred as a sequence of partial packets because of their length, there is a risk that different transfer routes via various gateways result in mix-ups or erroneous insertions of specific packet segments. The forwarding of data may also be delayed due to high load on a gateway. Another potential source of faulty data is electromagnetic interference, which may distort data, namely by “flipping” single bits or even by destroying entire information sections. Moreover, in networks where standard data as well as safety data are transferred, so-called “masquerades” can occur, i.e. standard data is taken to be safety data due to mix-ups and insertions. This may result in serious malfunctions.