Media gateway and automatic telephone call redirecting service system

An automatic call redirecting service system comprising an exchange capable of accommodating a plurality of Public Switched Telephone Network (PSTN) telephones and an IP call connection control server connected to an IP network,

• said exchange being provided with a built-in type media gateway connected to the IP network for performing conversion between voice signals and IP packets,
• said media gateway comprising a media gateway control unit connected to a control unit of the exchange, an IP network interface connected to the IP network, a first protocol processing unit for executing a call connection procedure according to a first call control protocol by communicating messages with said IP call connection control server via said IP network interface, and a second protocol processing unit for executing a call connection procedure according to a second call control protocol by communicating messages with said IP call connection control server via said IP network interface,
• said IP call connection control server comprising a data base for storing a plurality of entries each indicating a forwarding destination telephone number and a forwarding destination IP address in correspondence with a registered telephone number, and a server control unit for referring to the data base, upon receiving a call connection request from said media gateway, based on a called telephone number specified in the call connection request to judge whether the protocol of the call connection request is appropriate or not, depending on whether the called telephone number is registered in the data base and the type of the forwarding destination telephone number registered in correspondence with the called telephone number, and sending a connection protocol change command to said media gateway if it is judged that the call control protocol of the call connection request is inappropriate,
• wherein said media gateway control unit instructs said first protocol processing unit to start call connection processing according to the first call control protocol in response to a call connection command issued from said exchange control unit when a call is originated from any of said PSTN telephones, aborts the call connection processing of said first protocol processing unit while maintaining the connection between the PSTN telephone and the media gateway when receiving the connection protocol change command from said IP call connection control server via said IP network interface before completing the call connection according to the first call control protocol, and instructs said second protocol processing unit to start call connection processing according to the second call control protocol.

An IP call connection controller connected to an IP network, comprising:

• a data base for storing relations each indicating a forwarding destination telephone number and a forwarding destination IP address in correspondence with a registered telephone number;
• and
• a control unit for referring to said data base upon receiving a call connection request specifying a called telephone number from said IP network, based on the called telephone number specified in the call connection request to judge whether the protocol of the call connection request is appropriate or not, depending on whether the called telephone number is registered in the data base and the type of the forwarding destination telephone number registered in correspondence with the called telephone number, and
• sending a connection protocol change command to a node that sent said call connection request if it is judged that the call control protocol of the call connection request is inappropriate.