ic frequency selection and power users and access points; within 802.1x various authenti- control. cation algorithms with varying complexity and security However, the MAC layer is quite different. Instead of can be used. being based on the Ethernet standard, it is based on WPA uses a variant of the Temporal Key Integrity a totally different traffic approach, asynchronous transfer Protocol created by Cisco to improve security of the mode (ATM). ATM networking was developed by tele- packet encryption process. An initial 128-bit encryption phone service providers in the 1980s and 1990s in an key, provided in a presumably secure fashion using the attempt to provide a network that would support effi- 802.1 authentication process, is XOR'd with the send- cient transport of video, data, and voice, with control ing station's MAC address to provide a unique known key over the quality of service and traffic capacity assigned to for each client station. This unique intermediate key various users. Native ATM is based on fixed 53-byte is mixed with a 48-bit sequence number to create packets and virtual connections rather than the variable a per-packet key, which is then handed over to the WEP packets and global addressing used in IP networking over encryption engine as if it were composed of a 24-bit IV Ethernet. The HiperLAN MAC was constructed to and 104-bit WEP key. The sequence number is required provide a smooth interface to an ATM data network, by to increment on each packet, and any out-of-sequence using fixed time slots assigned to stations by an access packets are dropped, preventing IV-reuse attacks. The point acting as the central controller of the network. 48-bit sequence space means that a sequence number ATM was originally envisioned as extending all the will not be reused on the order of 1000 years at today's way from the WAN to the desktop but in practice has CHAPTER 5.1 Wireless local area networks seen very little commercial implementation beyond the case, with the passing of time the definition of a categor