For the last couple of years people have become too reliant on Wireless LAN (WLAN) for information exchange. As wireless technology has no inherent physical protection, WLANs introduce new serious security threats to the personal information of individuals and organizations. Unfortunately, much of the growth has not been accompanied with an appropriate level of security for most corporate networks. The broadcast nature of wireless networks promote casual eavesdropping of data traffic with possible security threats including unauthorized use of networks, and denial of service attacks etc. Therefore, as in any environment where data is transmitted over untreated media, in order to protect the data, certain safeguards must be in place and effectively managed. To this end, this paper introduces a wireless link layer security protocol for WLANs that provides the users of IEEE 802.11 WLAN a security level close to the security level of wired networks. The proposed security protocol consists of three components: WLAN clients (STAs), WLAN Access Points (APs), and Authentication and Accounting Server (AAS). Before an STA can access the network, the user who uses the STA must be authenticated to the AP. AP must be authenticated to the STA as well, so that there is no rogue AP in the network. Finally, the communication between STAs and APs, as well as between APs and AAS are protected and defended from any kind of interception, modification and fabrication. We performed extensive simulations to evaluate the security and energy consumption performance of the proposed security protocol. The cryptographic primitives are selected based on their security and power consumption to make proposed protocol scalable and a manageable solution for low power wireless clients, such as PDAs.