The invention relates to a method for transmitting real time-critical data using data messages in a data network. The data messages have an identification, useful data and a transfer status. According to the inventive method, data messages comprising errors are replaced by replacement messages that have the same structure as the data messages. The replacement message has the same identification as the data message to be replaced and is thus forwarded via the switching node, which would have been used to route the error-free data message. The replacement message can contain details of the type of transmission error.