A method for data transmission via data networks, in particular via ethernet-based data networks, having at least two participants; the data networks have at least one topological real-time field and one topological non-real-time field, and data telegrams sent via the data networks have at least one real-time part and at least one non-real-time part. By a coupling unit, data telegrams from the non-real-time field which arrive inside the real-time part are delayed and transmitted to the non-real-time part.