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http://www.nwfusion.com/buzz2001/nowires/ Fast LANs without the wires By John Cox Network World, 09/24/01 Wireless LANs are about to experience a boost that will give them enough throughput to handle all but the most bandwidth-hungry corporate applications. Yet security, network design and cost could be speed bumps to acceptance. By the end of this year, more than a dozen LAN vendors will introduce the first wireless LAN access points and interface cards based on the IEEE 802.11a standard, approved in 1999. These products will use the 5-GHz unlicensed radio frequency and reach a variety of speeds up to the 802.11a maximum of 54M bit/sec. By contrast, today's nets, based on the 802.11b standard (also approved in 1999) use the 2.4-GHz frequency and have a maximum speed of 22M bit/sec. Some vendors, such as Proxim, promise an optional and proprietary mode for their 11a products to boost speed to over 70M bit/sec. A radio modulation technique called Orthogonal Frequency Division Multiplexing (OFDM) is the source of 11a's higher speeds. OFDM divides one high-speed data carrier into 52 low-speed subcarriers that transmit in parallel. These subcarriers can be bunched much closer together than is possible with the frequency division multiplexing, spread spectrum technique used in 11b. So transmission is more efficient and yields higher data rates on 11a nets. Other differences between the specifications include radio ranges, antenna designs, security add-ons and network management features. To Top What to ask 802.11a wireless LAN vendors How can I migrate from 802.11b to your 11a products, and how will you minimize migration costs? Will your 11a products support the maximum 54M bit/sec speed specified by the IEEE standard? What additional wireless LAN security will you offer, particularly for stronger encryption and authentication, above that specified by 802.11a? Can I configure and manage access points and interface cards remotely, instead of manually? If so, how? What is the status of all necessary software drivers to support my mix of wireless client devices? Many of these differences will only be apparent, and measurable, in pilot tests. Because the same products can perform differently in different sites - depending on construction materials, user numbers and other variables - such pilots will be the only way to tell if you'd need more 11a access points than 11b, for instance. Theoretically, higher bandwidth means shorter range. But Rich Redelffs, president and CEO of 11a chip maker Atheros Communications of Sunnyvale, Calif., insists there is in fact little difference in range between the two, at least for 11a products based on the Atheros chipset. Both standards also share the same security issues. A wireless protocol sniffer can grab the wireless LAN network name, which works as a kind of network password, and it can grab unencrypted media access control (MAC) addresses, which identify nodes already authenticated on the wireless LAN. Most LAN card drivers let the card's MAC address be changed, so attackers could set their own card's address to be the same as a node already on the wireless LAN. Likewise, the Wired Equivalent Privacy encryption scheme used in 11a and 11b has been criticized for weaknesses that could let a sophisticated hacker decrypt the traffic. These security issues were spotlighted in August when three leading cryptographers discovered a relatively simple way of recovering the WEP encryption key, whic