A system and method for configuring a data communication between a terminal computing device and a communication network, wherein the terminal computing device connects to the communication network via a mobile device is tethered to a terminal computing device and acts as a wireless modem. A second handshake operation between the computing device and mobile device occurs after a handshake operation between the mobile device and network occurs to negotiate a variety of communication protocol parameters controlling the data communication. The variety of communication protocol parameters negotiated between the mobile device and network are used in the negotiation of communication protocol parameters during the second handshake operation between the computing device and mobile device.