Abstract: A method of providing a back up communications link for control messages within a delivery unit. The primary means of transport for both network data and control data within the delivery unit is by means of ingress and egress buses between application modules of the delivery unit. However, control messages from a unit controller can also be delivered by means of a separate link, typically to a bus control module.

Abstract: A system and method for managing faults in a data transmission system that includes a data path for transmitting signals containing data, and a plurality of application cards located along the data path for processing the signals. The method includes the steps of detecting the occurrence of a fault of a particular type at one of a plurality of points along the data transmission path; in response, the application card generating a fault report for the purpose of identifying the cause of the detected fault; and, preventing the generation by the application card of subsequent fault reports relating to that particular type of fault until receiving a signal indicating that fault report generation may be reenabled. In the fault management system, the data transmission system also includes at least one unit controller for controlling the application cards, and at least one system manager for controlling the at least one unit controller.