Abstract: When a failure occurs in the line of a communication network for transmitting packets using a tunnel, the disconnection messages of a plurality of tunnels which pass through the line are unified, and the occurrence of the failure is notified to an adjacent node for each line. Then, the tunnels are disconnected or switched based on a failure notice.

Abstract: Internet Protocol (IP) telephone number information system performs for the telephone number in the existing communication systems. A number information server in the system has a region information database representing an IP telephony service area for each of a plurality of Internet Service Providers (ISPs) having a corporate information database. The number information server specifies one of the plurality of ISPs from the region information database, based on a search condition input from a user terminal connected to the Internet. The specified ISP searches the corresponding corporate information database, and obtains number information matching the search condition. The number information server notifies the user terminal of the number information obtained from searching the corporate information database, in response to the search condition input from the user terminal.

Abstract: An ATM switch comprises a detector that detects impairments in signal lines, and a controller that controls the preservation of paths that have been established by call control via a signal line when an impairment has been detected on a signal line by the detector. When an impairment has occurred only on a signal line, interruptions in communications services are prevented by causing the data line paths to be preserved rather than released.