USB 3.0

Consider the situation that a GPRS subscriber of an operator in Finland is roaming in the U.S. and accessing a local service there. If the link layer mobility were used, the user’s IP packets would first be tunnelled to Finland, and then routed back to the U.S. In this scenario a round trip time from the mobile terminal to a server and back could be unacceptable to many services. As a solution to this problem, the roaming GPRS subscriber should use the services of a local GGSN in the visited network, allowing IP packets to be routed as soon as possible, without crossing over to the home network. As the IP address is now being assigned from the visited network, the mobile node would not be accessible via a network layer identity of the home network. For some applications this may not be a problem, but in general it would be desirable if the mobile node could be reached with an IP address being assigned from the home network as well. A natural solution to this problem is to use Mobile IP to register the visited network address with the home network, allowing packets sent to the home address to be delivered to the mobile node.