Token ring network test device using finite state machine

A system that monitors a local area network by receiving all messages transmitted over the local area network, and analyzing selected sequences of messages to determine if certain, architecturally defined, processes are properly completed. If a network station starts one of these processes, and the process does not complete normally, the system analyzes the messages involved in the process to determine the network stations that participated in the process, and the phase or phases of the process that were completed. This allows the system to provide information to a user of the system that identifies a possible cause for the process not completing, and a possible network station or stations likely to be at fault.