Affordable Wireless LAN Using Airport
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Reliability and speed
You may be wondering how much speed you have to sacrifice in order to gain portability. You'll be happy to hear that the Airport wireless network can transfer data up to 11 megabits per second (Mbps). The software interface includes a nifty "signal level" indicator that shows you the strength of your connection. In my home environment, it averages 80 to 90 percent of the maximum 11 Mbps.
Since Airport sends information via radio waves, there's always the possibility of signal interference. Base stations have 10 channels to choose from if interference becomes an issue. Devices that can cause interference include microwave ovens, 2.4 gigahertz phones, and RF leakage from direct satellite service.
Also keep in mind that some building materials can affect Airport communication. Typically, wood, plaster, and glass have very little impact on Airport communication. On the other hand, concrete and metal will most likely degrade performance. Bricks and marble fall somewhere in between.
One final word of advice: don't use the Airport card in an airport or on a plane. If the airlines are concerned about interference from a portable CD player, imagine their views on radio frequencies broadcasting up to 150 feet!
Two Levels of Security
Apple uses the "silver" version of the Lucent communications card which adheres to the 802.11 cross-platform standard and has 40-bit encryption. You can create an additional level of security on your wireless network (called Access Control) by only allowing computers with specific IDs to log on. Each Airport card has a unique ID number stamped on the outside. By listing the ID numbers of the computers that you will allow on your network, you can control participation. Access Control can handle up to 497 client computers.
If you don't know your Airport ID number, don't worry. Simply launch the Airport application and click the button reading "Turn Airport On." Once Airport is activated, you can read your 12-digit alphanumeric ID in the status area.
Computer to Computer Access
Taking a page out of the Napster/Freenet book of philosophy, Airport-enabled computers can communicate directly with each other even when they're away from a Base Station. Apple calls it a computer-to-computer connection.
This function is especially handy for setting up a multiplayer game network or for encrypted file sharing. Not that anyone ever attends a boring company meeting, but if one did occur, Mac-toting attendees could spontaneously set up a network and exchange notes or play a game to pass the time.
To do so, both parties simply set their Airport configuration to "computer-to-computer." Each active computer appears by name in the Airport control screen, and the connection is activated by simply choosing the computer you want to engage.
Internet connections via Airport require standard Internet protocols such as PPP. This is fine for most users. The most likely exception to standard protocol would be logging on via America Online, which uses non-standard access. Also, some DSL providers use PPoE protocol which can also cause Airport connection problems. It's best to check with your ISP before purchasing Airport hardware.
Cross Platform LAN
Because Airport uses cross-platform standard 802.11 protocol, a Windows/Mac wireless network is possible -- at least in theory. We're going to try to establish just such a network at O'Reilly. Our next article will report the outcome and delineate the procedure -- if we can make it work.
In the meantime, Mac users who have Airport-enabled machines might want to consider setting up a wireless LAN. There's nothing quite like taking your PowerBook out to the patio on a beautiful day to finish up that last bit of e-mail correspondence. You'll be the envy of everyone in the office.
Derrick Story is the author of The Photoshop CS4 Companion for Photographers, The Digital Photography Companion, and Digital Photography Hacks, and coauthor of iPhoto: The Missing Manual, with David Pogue. You can follow him on Twitter or visit www.thedigitalstory.com.
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