Gateway carrying out routing optimization

摘要

A gateway is connected to the Internet and a telephone exchange which carries out routing optimization based on a first message and accommodates a plurality of terminals. The gateway includes: a call setting means used for determining an IP (Internet Protocol) address of a second gateway serving as a called communication partner on the basis of a second message serving as a request for call setting and used for opening a control channel to the second gateway by transmitting a third message to the second gateway at the IP address by way of the Internet; a first message transmitting means for transmitting a fourth message received from the connected telephone exchange to the second gateway by using the control channel; a second message transmitting means for transmitting a fifth message to the connected telephone exchange when receiving the fifth message transmitted by another telephone exchange connected to the second gateway through the control channel by way of the second gateway; an audio-channel opening means for opening an audio channel; and a channel releasing means for releasing the control channel and the audio channel.