The IEEE 802.11i amendment has been finalized to address the security issues in wireless local area networks. A prodigious amount of research has demonstrated that the IEEE 802.11i specification is sufficient to prevent unauthorized access and use. In this paper, we analyze the IEEE 802.11i wireless networking amendment with respect to data confidentiality, integrity, mutual authentication and availability. Our analysis indicates that a number of serious threats have still not been addressed by the 802.11i amendment. This includes DoS attacks, insider attacks, offline guessing attacks, etc. Furthermore, configuring security features on a commercial Wi-Fi network is moderately-to-very difficult. Towards this end, this paper proposes an improved authentication mechanism which adopts asymmetric cryptography and thus accomplishes link-layer frame protection. Through our further analysis and discussion, we conclude that the proposed mechanism not only prevents potential security threats but also accomplishes autonomic security configuration without human intervention.