Abstract: The network address translation system in a Global System for Mobile Communications network isolates internal IP traffic from external IP traffic in the Inter-Working Function (IWF) of a Global System for Mobile Communications network by assigning dual IP addresses for the Inter-Working F unction Protocol Engine. The Inter-Working Function Protocol Engine includes one or more Ethernet Ports, each of which is assigned a private IP address, to connect to the Ethernet Switch as well as a public IP address of the customer's network, used to connect to L2TP Network Server.

Abstract: The Direct Internet Access system makes use of an L2TP/UDP/IP connection to the Internet via a L2TP Network Server and the existing Local Area Network or Wide Area Network of the cellular communication network. This system uses a Layer 2 Tunneling Protocol which provides a virtual dial-up access to corporate gateways by extending the dial-up connection that is established between the mobile subscriber station and the Mobile Switching Center to the Internet or a corporate gateway over the Internet. The user has an L2 connection to an access concentrator in the Mobile Switching Center, which then tunnels individual Point-to-Point Protocol frames to the L2TP Network Server, so that the packets can be processed separately from the location of the circuit termination. This means that the mobile subscriber station call connection can terminate at a local circuit concentrator in the Mobile Switching Center, eliminating possible long-distance charges, among other benefits.