Mobile IP Authentication is a requirement for the TR 45.6 CDMA wireless packet data service architecture[8]. Diameter AAA, as described in [1] and [2], is used to support Mobile IP authentication. This requires that both the foreign and home network deploy Diameter servers. Currently, RADIUS servers have been deployed and are widely used in the Internet Service Provider(ISP) arena.While DIAMETER is required to provide the advanced AAA support required by the TR 45.6 architecture, a smooth transition from RADIUS AAA to Diameter AAA is required. At a minimum,the Diameter AAA server located in a foreign network must inter-operate with RADIUS AAA located in Home Network.