Double ring network system and communication control method thereof, and transmission station, and program for transmission stations

A double ring network system including transmission stations provided with a first communication port and a second communication port each adapted for bi-directional communications and connected in a ring form through a transmission line, having among the transmission stations a base station transmitting frame signals via a right-handed route and a left-handed route, and a terminal station of the right-handed route and a terminal station of the left-handed route returning frame signals from the base station, respectively, wherein

• the transmission stations, the terminal stations, and the base station each respectively comprising:
• means for determining whether or not frame signals are received at a first communication port adapted for communications by the right-handed route, and a second communication port adapted for communications by the left-handed route;
• means for transmitting route identifying frame signals for identification of routes from the first and second communication ports to adjacent transmission stations, when having failed in reception;
• and
• means for setting own station as a terminal station, when having received no responses to the route identifying frame signals from the adjacent transmission stations.

A communication control method for network systems including transmission stations provided with a first communication port and a second communication port each adapted for bi-directional communications and connected in a ring form through a transmission line, having among the transmission stations a base station transmitting frame signals via a right-handed route and a left-handed route, and a terminal station of the right-handed route and a terminal station of the left-handed route returning frame signals from the base station, respectively, and responding to occurrence of an anomaly on any transmission line by setting new terminal stations, wherein

• for a respective one of the transmission stations, the terminal stations, and the base station, the method comprising:
• a process of determining whether or not frame signals are received at a first communication port adapted for communications by the right-handed route, and a second communication port adapted for communications by the left-handed route;
• a process of transmitting route identifying frame signals for identification of routes from the first and second communication ports to adjacent transmission stations, when having failed in reception;
• a process of setting own station as a terminal station, when having received no responses to the route identifying frame signals from the adjacent transmission stations, and
• a process of keeping a right-handed frame signal from the base station from being transmitted to a subsequent adjacent right-handed transmission station, as own station is set as a terminal station on the right-handed route, or from being transmitted to a subsequent adjacent left-handed transmission station, as own station is set as a terminal station on the left-handed route.

A transmission station interposed between transmission lines of a double ring network system and provided with a first communication port right-handed communicative and a second communication port left-handed communicative, comprising:

• means for determining whether or not frame signals are received at the first communication port communicative via a right-handed route and the second communication port communicative via a left-handed route;
• means for transmitting route identifying frame signals for identification of routes from the first and second communication ports to adjacent transmission stations, when having failed in reception;
• means for setting own station as a terminal station, when having received no responses to the route identifying frame signals from the adjacent transmission stations, and
• means for keeping a right-handed frame signal from a base station from being transmitted to a subsequent adjacent right-handed transmission station, as own station is set as a terminal station on the right-handed route, or from being transmitted to a subsequent adjacent left-handed transmission station, as own station is set as a terminal station on the left-handed route.

A non-transitory computer readable medium storing a program for control of communications for double ring network systems including a first communication port right-handed communicative and a second communication port left-handed communicative interposed between transmission lines of double ring network systems, for having a computer implement functions as:

• means for determining whether or not frame signals are received at the first communication port communicative via a right-handed route and the second communication port communicative via a left-handed route;
• means for transmitting route identifying frame signals for identification of routes from the first and second communication ports to adjacent transmission stations, when having failed in reception;
• means for setting own station as a terminal station, when having received no responses to the route identifying frame signals from the adjacent transmission stations, and
• means for keeping a right-handed frame signal from the base station from being transmitted to a subsequent adjacent right-handed transmission station, as own station is set as a terminal station on the right-handed route, or from being transmitted to a subsequent adjacent left-handed transmission station, as own station is set as a terminal station on the left-handed route.