Patent US 4,939,724

A link (19) connects a first controller (6) and a second controller (10) in a local area network. The second controller sends a header to the first controller (6) containing status information as to the status of an input buffer (70) at the second controller. The flow of the message data from a first buffer (44) at the first controller is controlled depending upon the status of the input buffer (70) at the second node. This prevents overflow of the input buffer (70) by controlling the rate at which new messages are placed on the transmit data link (19).