Patent ID: 8842521

Claim:
A communication management apparatus that manages transmission of data in a token passing system in a network in which a plurality of communication nodes are connected via a transmission line in a ring shape, the communication management apparatus comprising: two ports connected to, via the transmission line, the communication nodes adjacent to the communication management apparatus; a line-connection managing unit that gives an instruction for switching a port of any one of the communication nodes on the network including the own apparatus to a disabled state in which frame transmission and reception is impossible and an enabled state in which frame transmission and reception is possible; a network-presence checking unit that transmits, in broadcast, a network presence check frame for recognizing the communication node present in the network, receives a network presence check acknowledge frame including a relation between a communication node adjacent to the communication node and ports of the communication node, and performs network presence check processing for generating network connection information indicating a connection state between the communication nodes; a token-circulation-order determining unit that determines token circulation order using the network connection information; a setup processing unit that performs, based on the token circulation order, setup processing for notifying each of the communication nodes in the network of a communication node to which a transmission right is granted after the communication node; and a data-frame-communication processing unit that performs transmission and reception of a data frame using a token frame, wherein when the line-connection managing unit recognizes, according to the network connection information, that the network has a ring configuration, the line-connection managing unit disables any one of ports of any one of the communication nodes in the network to prevent a connection state of the network from becoming a ring shape.