This paper focuses on the integration of Internet and Wireless LANs (WLANs) and proposes a novel technique that supports seamless and efficient integration. This technique is based on a generic adaptation layer, referred to as Wireless Adaptation Layer (WAL), which is introduced between the IP layer and the WLAN Link Layer. WAL is designed to (i) dynamically cope with the wireless channel impairments, (ii) provide QoS interworking between the IP infrastructure and the WLAN and (iii) be independent of the WLAN technology. These characteristics account for the advantages of WAL, namely, the improved performance, the wide applicability and the provisioning of differentiated services.