SWITCH DEVICE, RING NETWORK SYSTEM, COMMUNICATION CONTROL METHOD, AND PROGRAM OF DEVICE

PROBLEM TO BE SOLVED: To detect the generation of a loop using periodical control frames specified in a protocol prescribed to prevent the generation of the loop to transmit notification information, even when prevention of the generation of the loop by the protocol does not function due to runaway of software and a failure of a CPU or the like, in a system using the protocol. SOLUTION: A switch device includes a transmission means for periodically transmitting the control frame prescribed in a standard to a ring network, when source address information in a received frame matches to address information of the transmission means in a received communication line, and the received frame which is the source address information is the control frame, a loop detection means detects it as the generation of the loop. When the generation of the loop is detected by the loop detection means, a notification information transmission means transmits notification information for notifying the generation of the loop. COPYRIGHT: (C)2011,JPO&INPIT