The invention relates to a time-controlled distribution unit (30, 31) for the distribution of messages in a distributed computer system for safety-critical applications. Said distribution unit is designed as a self-testing functional unit and comprises input channels (201 . . . 222) for receiving time-controlled periodic input messages from node computers (20, 21, 22) upstream in the data flow, and output channels (301 . . . 333) for transmitting time-controlled periodic output messages to the node computers (50, 51, 52) downstream in the data flow, a computer (40) being provided in the distribution unit and being designed to analyze, by means of a “simple” software, useful information contained in the input messages, and to decide whether output messages are output and, if so, which useful information is contained in the output messages.