A wireless services data network supporting the mobility of an Internet Protocol (IP) over ATM networks is implemented such that a joint ATM-layer hand-off and MAC-layer hand-off are respectively used to handle in-session and inter-session mobility. In this way the effect of mobility is localized and transparent to higher-layer protocols. Also, different functions, including the so-called Address Resolution protocol, location of a mobile, and ATM connection, are combined to reduce front-end delay for connectionless packet transmissions in connection-oriented ATM networks.