Method for transmitting facsimile data between facsimile apparatuses through an internet protocol network and relay apparatuses used in the method

A method for transmitting facsimile data between a facsimile apparatus of a sending side and a facsimile apparatus of a reception side, the facsimile apparatus of the sending side being connected to a relay apparatus of the sending side, the facsimile apparatus of the reception side being connected to a relay apparatus of the reception side, and the relay apparatus of the sending side being connected to the relay apparatus of the reception side through an internet protocol network, comprising steps of:

• performing an address conversion from a telephone number of a facsimile apparatus of the reception side, which is transmitted from a facsimile apparatus of the sending side when setting a call, to an IP address corresponding to the telephone number;
• transmitting a request for establishment of TCP connection including a flow control and re-transmission function, to a relay apparatus corresponding to a destination of the IP address, when receiving an identifying signal which indicates transmission of the facsimile data from the facsimile apparatus of the sending side;
• and
• transmitting the facsimile data to the relay apparatus corresponding to the destination of the IP address based on the TCP connection.