Communication is performed without paying attention to the fact that the
communication is executed between multimedia terminals having
communication procedures differing from each other.A terminal 2 starts a
communication procedure that is necessary to establish a communication
path to a communication service unit 1, in order to execute communication
with a multimedia terminal 3; when a communication protocol conversion
unit 7 receives communication start request from the terminal 2, the
communication service unit executes identification process of a calling
terminal based on the identification number, which exists in
communication start request, for determining the multimedia terminal 2,
and inquires a terminal information managing unit 9 of the calling
terminal. The terminal information managing unit 9 retrieves terminal
information related to the calling terminal based on a terminal
information request, and informs of the retrieved terminal information to
the communication protocol conversion unit 7. The communication protocol
conversion unit 7 informs of the communication start request to the
terminal 3 when the transmitting the terminal information of the terminal
2 is obtained, and continues a relay process in communication procedure,
which is necessary for following establishment of a communication path.