A mobility agent returns a registration reply message to a mobile node that has sent a registration request message. If the mobile node requests service from a foreign agent, that foreign agent receives the reply from the home agent. Subsequently, the foreign agent relays the reply to the mobile node. The reply message contains the necessary codes to inform the mobile node and the foreign agent about the status of the registration request. The message also contains the lifetime that is granted by the home agent. The lifetime can be smaller than the original request. The registration reply can also contain a dynamic home address assignment.