Abstract: A multi-nodal data processing system includes a plurality of processing nodes, each node connected to plural other nodes by bidirectional data links. Each node comprises receivers for receiving messages on bidirectional data links and transmitters for transmitting messages on bidirectional data links. Each node records child nodes to which a message was transmitted and is further adapted to transmit a lock-up message received from a child node to a parent node, the lock-up message indicating a successful establishment of a message signal path to a destination node. Each node further is adapted to transmit a link cancel signal to another node to close the link in the event of an unsuccessful message transfer attempt over the link. Each node inhibits transmission of a lock-up signal to a parent node until link cancel signals have been received from all child nodes (other than a node from which a lock-up signal was received).

Abstract: 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.sub.-- link control code. The torus sends the test.sub.-- link code to the neighboring 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.