What Mac users need to know about Wi-Fi Direct

It’s that time of year when travelers brace themselves to suffer the many small indignities of the road. Why can’t it be easier to print on networks that you don’t have regular access to or transfer files among mobile devices like iPhones? Why is it such a pain to create secure, robust networks with colleagues or friends on the fly using 3G mobile broadband as the Internet connection? A new wireless networking system, Wi-Fi Direct, will soon help Mac users do all that and more. It lets any wireless device maintain a connection to a network base station while also communicating directly with other devices that aren’t on the same network. And it’s (probably) coming soon.

The Wi-Fi Alliance announced Wi-Fi Direct in October. The technology will start showing up in hardware and software by mid-2010. Operating system makers like Microsoft and Apple—though they sit on the board of directors of the trade group responsible—haven’t yet signaled their support or a firm timetable for including the technology in new equipment. It’s possible that adapters in a lot of 2008 and 2009 computers and mobile devices will be upgradable, but we don’t know for sure yet. Here’s what we do know:

It'll be a big improvement over what we have now

In the current scheme of things, Wi-Fi networks come in two flavors: infrastructure, which relies on one or more base stations connected to the Internet, and ad hoc, where two or more computers join together over short ranges. (You can turn a computer into a software base station, too, but the OS X 10.2 to 10.6 implementation can’t do much when compared to a hardware base station.)

Ad hoc Wi-Fi’s flaws An ad hoc connection would seem to do what Wi-Fi Direct promises. But this kind of connection has a host of flaws, starting with poor security options, low speed, and incompatibility. Ad hoc mode has never been standardized or put through a testing and certification program like infrastructure mode has. This can make it difficult or impossible to use the mode between computers running different operating systems or even different wireless networking hardware.

In ad hoc mode, computers broadcast the same network name with a flag that indicates it’s a computer-to-computer network. With no central coordinating hub, each computer has to listen for broadcasts. That means file transfers and communication tend to crawl along at a fraction of the possible speed.

Apple’s version of ad hoc networking—available from the Create Network item in the AirPort menu—doesn’t allow you to use robust security. It instead relies on the outdated WEP (Wired Equivalent Privacy) encryption standard. (WEP keys can be cracked in between one and fifteen minutes by someone using free software. Once the person is in, he or she can intercept all data on the network or connect to the network.)

Further, you can only select from 2.4GHz Wi-Fi channels. The 2.4GHz band is the only band that the original AirPort (802.11b) and AirPort Extreme (802.11g) adapters and base stations can use. This band is full of interference. Many other communications devices use it—anything using Bluetooth, cordless phones, base stations, and even some baby monitors. Microwave ovens use a 2.4GHz signal to heat food, emitting noise while active. Industrial, scientific, and medical devices also use the 2.4GHz band. The 2.4GHz band is often known as a “junk” band because of all this jostling and crowding. (For more on spectrum choices, see “Understanding Wi-Fi’s two spectrum bands.”)

Software base station’s flaws Apple also offers a software base station, which was added way back in the Mac OS 8 days, but which disappeared between OS X 10.0 and 10.1; it returned in 10.2. To configure and turn on the software base station, open System Preferences, click on Sharing and select Internet Sharing.

If you choose to share a network connection via AirPort, Mac OS X turns on a software base station and your computer becomes a central Wi-Fi hub. However, the AirPort Options dialog box presents nearly identical options as you’d see for an ad hoc network. And you can’t be connected to a Wi-Fi network and share it with other Wi-Fi clients at the same time.

The technology promises a lot

Here’s a common scenario: You’re traveling with one or more people. You have a fast 3G USB modem for your computer and you’d like to share that 3G connection. Today, you could use either ad hoc networking or the software base station to let your colleagues or friends hook up. But you’d suffer from all the problems I’ve talked about here. With Wi-Fi Direct, other people can connect to your laptop with a high degree of security and simplicity.

Easy connections The protocol includes “service discovery.” In other words, when you try to connect with a Wi-Fi Direct enabled device, you’ll see a connection menu that sums up what it can do. For instance, you might see “printing” or “Internet access” listed as options next to a network name. Today’s Wi-Fi networks only show the network’s name.

Strong security Wi-Fi Direct supports the modern Wi-Fi Protected Access 2 (WPA2), the full wireless security standard that Apple has supported for Wi-Fi infrastructure purposes since 2005. All 2003-and-later base stations and all AirPort Extreme Cards in Panther or later could be updated for WPA2 if they weren’t shipped with such support already turned on. (The original WPA was backwards compatible with older gear, and AirPort Cards could be updated, although not the original 802.11b base stations. WPA2 required additional hardware, limiting support to 2003 and later cards and base stations.)

When you select a network to join, Wi-Fi Direct will initiate a special simplified security connection using Wi-Fi Protected Setup (WPS). A typical scenario will have you press a button on a printer or click a button in onscreen software on the device to which you want to connect to confirm access. Then a secure process exchanges strong WPA2 keys. (It may be implemented the other way around, too: press a button in software or hardware on the device to which you want to connect, then try to join the network; that’s not clear yet.)

Versatile connections One of the key differences between existing Wi-Fi connection methods and Wi-Fi Direct is that a single Wi-Fi adapter can maintain a connection to a base station while also connecting to other devices in this peer-to-peer fashion.

While some of these features may sound a lot like Bluetooth, Bluetooth is a slow way to connect. It’s designed for peripherals that have very little room for batteries, and is already found in hundreds of millions of handsets worldwide. Bluetooth will become faster in mid-2010, using 802.11g for up to 25Mbps for data transfers. But even that new version is keyed more towards device-to-device and peripheral connections rather than network connections or very large transfers.

Speed Wi-Fi Direct will work with the far less frequently used 5GHz Wi-Fi channels, which can carry data at much higher rates than 2.4GHz because of a lack of interference and the ability to employ “wide” channels that use twice the frequency range. (Technically, you can have wide channels in 2.4GHz, but the lack of spectrum in that band makes it impractical. Apple doesn’t even include the option.)

Glenn Fleishman is a regular contributor to Macworld, and the author of Take Control of Your 802.11n AirPort Network, recently updated for Snow Leopard

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