The Gp Interface connects PLMN (Public Land Mobile Network) together. This interface is IP based and must support appropriate routing and security protocols to enable a subscriber to access its home services from any of its home PLMN’s roaming partners. Many GPRS operators/carriers have abstracted these functions through the GRX (GPRS Roaming eXchange). This function is typically provided by a 3rd party IP network offering VPN (Virtual Private Network) services that connects all the roaming partners together. The GRX service provider ensures all aspects of routing and security between the networks are optimized for efficient operation.