As WEP has been shown to be vulnerable to multiple attacks, a huge effort has been placed on specifying an access control mechanism to be used in wireless installations. However, properties of the wireless environment have been exploited to perform multiple DoS attacks against current solutions, such as 802.11/802.1X. In this paper we discuss the main wireless idiosyncrasies and the need for taking them into account when designing an access control mechanism that can be used in both wireless and wired networks. We present the design of a mobility-aware access control mechanism suitable for both wireless and wired environments and show how the DoS attacks discussed can be prevented by implementing secure association and other essential services. The architecture proposed here, composed of the SIAP and SLAP protocols, uses public keys together with the RSA and AES encryption algorithms to provide a flexible service.