METHOD FOR FACILITATING COUNTERMEASURE TO FAILURE IN VoIP SYSTEM AND VoIP SYSTEM AND COMMUNICATION SWITCH MANAGING DEVICE FOR VoIP SYSTEM

摘要

PROBLEM TO BE SOLVED: To preliminarily inform a user that transmission through a VoIP line is unavailable, or to realize communication through the VoIP line as much as possible when a gate keeper is not operating. SOLUTION: A communication switch managing device connected to an IP network transmits a pseudo inquiry for an IP address to a gate keeper with arbitrary time intervals in order to grasp the operating state of the gate keeper. At the time of grasping that the gate keeper is not operating, the device informs a plurality of communication terminals of the result. Those communication terminals inform a user that a VoIP line is unavailable by flashing a key for transmission through the VoIP line with prescribed intervals. When this device is provided with a mode enabling the communication through the VoIP line without using the gate keeper, it is automatically switched to the mode.