Patent ID: 6888793

Claim:
An Internet protocol network alternate routing system comprising: an extension telephone; a plurality of networks including one Internet protocol network for transmitting voice signals from said extension telephone; an exchange for controlling a connection between said extension telephone and said plurality of networks; and an announcement trunk for reporting switching of said connection between said extension telephone and said plurality of networks when the Internet protocol network is determined by said exchange to be in a congested state; wherein said exchange, upon detecting a state of congestion over a first link of said Internet protocol network on which said extension telephone is connected, automatically switches said extension telephone to a second network, said second network being other than said Internet protocol network; wherein said exchange comprises: a plurality of signal paths for connecting said plurality of networks with said extension telephone; an alternate routing control unit for determining which one network among said plurality of networks is to be connected as said second network with said extension telephone; a call control unit for establishing a second link between the second network that has been determined by said alternate routing control unit and said extension telephone; a traffic control unit for detecting a congested state of said Internet protocol network for which said first link has been established by said call control unit; a switch control unit for controlling said connection between said extension telephone and a signal path among said plurality of signal paths that is connected to the second network, based on detection results in said traffic control unit; and a voice converter that, when said first link has been established with a partner node by said call control unit and voice signals are transmitted from said extension telephone by way of said switch control unit, converts the transmitted voice signals to packets, assigns port numbers to each of the packet voice signals, and outputs the voice signals as outputted voice signals; wherein said traffic control unit adds Internet protocol addresses that are outputted from said call control unit to said outputted voice signals outputted from said voice converter to generate and output Internet protocol packets as outputted Internet protocol packets; and wherein said exchange further comprises: an RTP (Real-time Transport Protocol) unit for adding RTP headers to said outputted Internet protocol packets outputted from said traffic control unit and outputting the header-added Internet protocol packets; and a network driver for transmitting on said Internet protocol network said header-added Internet protocol packets outputted from said RTP unit.