Disclosed is a protocol embodying system and method in the GGSN. An IP layer is provided between the GPRS network and the PDN and performs routing between the two networks, and performs routing between the protocols of the first and second network layers and the transfer layer protocol on the GPRS network. A virtual driver is provided on the lower part of the IP layer, is connected to the protocol of the GPRS tunneling provided to the upper part of the IP layer on the GPRS network, and is operable as the lower interface of the IP layer. Since the upper part and the lower part of the IP are appropriately connected by the virtual driver, a single IP is needed in the system, and the embodied configuration becomes simpler.