1. A method of scheduling messages being transmitted on a network among spatially-distributed control components of a distributed real-time control system, wherein the messages are associated with a control task performed by the control components to control an industrial process and wherein the messages are periodically transmitted, the method comprising: receiving a current transmission of the periodically transmitted message; receiving a relative timing constraint concerning the message from one of the current message and an execution history, wherein the relative timing constraint is indicative of an amount of time to complete processing of the message; receiving a priority associated with the message; determining if a network bandwidth limit for the message can be met; inserting the message into a queue for transmission over the network upon determining that the network bandwidth limit can be met, wherein the message is inserted into the queue at a location that is a function of the priority and of the relative timing constraint, and preventing the message from inserting into the queue upon determining that the network bandwidth limit cannot be met; and storing an execution period of the current message in the execution history.