| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To solve the problem that a call control server cannot correspond to the requirement of a call-control service offer capable of being generated from an IP telephone and an availability is deteriorated at all times when a time required for changing over systems, the time until a database server can be utilized actually after the start of a utilization is required to the database server as a standby system up to that time by the call control server is lengthened. <P>SOLUTION: A communication system is used for continuously utilizing a server device by a client device. In the communication system, the client device previously ensures a connection to a living system server device currently utilized by the client device and a standby system server device not utilized currently, carries out the changeover of the systems and utilizes the standby system server device when the unpractical state of a normal communication with the living system server device is detected. The connection is ensured simultaneously regarding a plurality of protocol hierarchies, whether or not the normal communication cannot be practised is inspected independently at every protocol hierarchy and it is preferable that the systems are changed over when the normal communication cannot be practised by either one protocol hierarchy. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
