Transmission control apparatus and method for TCP/IP protocol group

A transmission control apparatus of the present invention includes a reliable service unit for providing reliable peer-to-peer data communication at layer 2 of a TCP/IP stack, and a setup unit for setting the reliable service unit. The reliable service unit includes a fragmentation part for fragmenting a service data unit (SDU) from an upper layer into protocol data units (PDUs) of a predetermined length, a sending buffer for temporarily storing the PDUs from the fragmentation part, a receiving buffer for temporarily storing PDUs received through a communication channel, a reassemble part for assembling the PDUs stored in the receiving buffer to a SDU of the upper layer, a poller for controlling data transmission/reception by checking network conditions, and a control unit for controlling at least one of the fragmentation part, sending buffer, receiving buffer, reassemble part, and poller. A transmission control method of the present invention includes initializing reliable peer-to-peer data communication at layer 2 of a TCP/IP stack, registering ports of the transmission control apparatus and devices to be connected to the ports, determining whether there is an upper layer SDU to be sent, transmitting the upper layer SDU, determining whether there are lower layer PDUs to be received when no upper layer SDU exists to be transmitted, and receiving the lower layer PDU if there are lower layer PDUs to be received.