AAA servers, in use within the Internet, provide authentication and authorization services for dial-up computers. These services are likely to be equally valuable for mobile nodes using Mobile IP when the nodes are attempting to connect to foreign domains with AAA servers. AAA servers identify clients by using the Network Access Identifier (NAI). A mobile node can identify itself by including the NAI in the Mobile IP registration request.
Since the NAI is typically used to identify the mobile node uniquely, the mobile node's home address is not always necessary to provide that function. Thus, it is possible for a mobile node to authenticate itself, and be authorized for connection to the foreign domain, without even having a home address. To request that a home address be assigned, a message containing the mobile node NAI extension can set the home address field to zero in the registration request.