A system for processing protocols for Internet services employing a serial line and an asynchronous transfer mode (ATM) network, including a settop-box for loading transmission control protocol/Internet protocol (TCP/IP) data on a designated ATM cell or delivering TCP/IP data loaded on an ATM cell to a computer, and an Internet gateway for converting the data according to a protocol used in an external network into the TCP/IP data transferred through the settop-box and the ATM network, wherein the Internet gateway also converts the TCP/IP data into the data according to the protocol used in the external network.