Method and apparatus for testing links between network switches

A test link protocol which continuously monitors each link in a network to ensure that the link is correctly transmitting data. Each switch, or torus has at least one of two functional components: Send Test and Receive Test. The Send Test component monitors control codes at a torus link output. The Receive Test component monitors control codes at a torus link input. After a predetermined interval, the Send Test component makes a request to send a test_link control code. The torus sends the test_link code to the neighbouring torus, where it is removed from the data stream and sent to that torus' Receive Test. The Receive Test then generates a response message and makes a request to send that message back to the originating torus. After receiving the message, the Send Test analyzes the message to determine whether the network link is working correctly. An error is also declared if the Send Test does not receive a reply within a predetermined interval.