Patent ID: 8397243

Claim:
A relay connection unit, to be mounted on a car, which is interposed between communication lines connecting electronic control units (ECUs) thereto and which relays messages to be sent and received among said ECUs belonging to different communication lines, said relay connection unit comprising: a processor and a memory, the processor programmed to function as: a buffer part temporarily storing said messages in order of reception; a storing part storing a priority set in advance for each of said messages and a counter M initially set to a value equal to 1; and a processing part that: takes out N messages stored by said buffer part in order of reception, from a front message to an Nth message, reads said priority of each of said N messages taken out of said storing part, sequentially compares a priority of the front message with a priority of each of said other N messages in order of reception, sends a message of said N messages with the highest priority, removes said sent message of said N messages from said buffer part; increments variable M by 1; and compares the variable M with said N messages.