Ad Hoc Networks

By Sean Gallagher  |  Posted 2001-12-10

What are they?

Temporary, short-range networks created when devices using the same protocol connect. Typically based on short-range wireless technology, these networks don't require subscription services or carrier networks. When you beam a business card from your PDA to another, or use an IrDA port to print from your laptop to a department printer, you've formed an ad hoc network.

PDF DownloadWhy would you care?

Reduced costs and improved security. After the initial device configuration, ad hoc networks are generally administration-free: Users can connect to resources, and to one another, without a lot of wire-pulling. The downside is that the explosion of PDAs and advanced mobile phones carrying corporate data has created a data-management nightmare. Enforcing a sensible policy for ad hoc networks can change these devices from islands of information out of the company's control into good IT citizens that can be synchronized with desktops and databases.

How do they work?

By the strictest definition, an ad hoc network is one formed without the use of an access point or a server. To join in an ad hoc network, devices need hardware with which to connect—a wire (like Ethernet or USB), an infrared (IR) port or, increasingly, a spread-spectrum radio frequency (RF) chip. Many devices today support cable or IR connections. The majority of new ad hoc networking development, however, is happening in the RF realm.

The furthest along of the RF technologies, Bluetooth and WiFi, depend on the IEEE's 802.11 standard, which provides ways to referee network requests.

Bluetooth devices each have a unique, built-in ID. They can communicate at a range of up to 30 feet, generally at speeds around 700 Kbps to 800 Kbps (slower than a wired network but faster than a serial cable). They use a small amount of power and, unlike IR connections, don't require a line of sight between devices. Already used in mobile phones from Nokia and Ericsson and expected in the next generation of PDAs, Bluetooth's adoption has been hampered by complexity, intellectual property issues and security concerns.

WIFI (a.k.a. IEEE 802.11b) supports device-to-device networks as well as client-server networks comprised of wireless hubs or access points. WiFi, which can transmit at up to 11 Mbps, behaves like Ethernet—it interoperates with existing network protocols like TCP/IP and with applications like file sharing and Web browsing. The current generation of hardware consumes too much power to be practical for use with smaller devices and has security holes that can cause major problems for corporate LANs.

Are there security problems?

Bluetooth devices may not connect directly to your corporate network, but users can synchronize them to a computer on the LAN. A user might unknowingly corrupt data or spread a virus during synchronization, or someone else with a Bluetooth device might be able to jump in and pluck passwords. Conversely, a user that downloads corporate information puts that information at risk if he synchronizes in an insecure environment.

WiFi's longer range—and the fact that it is usually connected to the corporate LAN—poses a greater potential security problem. Someone in your parking lot could conceivably get onto your LAN. And even if someone doesn't attempt to connect to the LAN over WiFi, he could use a wireless "packet sniffer" to capture data traveling across it.

What does the future hold?

Converging protocols, converging devices. The most promising is the IEEE's upcoming 802.15 standard for Wireless Personal Area Networks. Although 802.15 will itself be a new wireless standard, the working group is focusing on compatibility with Bluetooth and WiFi. The 802.15 standard will also support low-data-rate, low-power devices like intelligent badges, remote controls and environment-automation devices.

Background Reading

Find out what the IEEE is planning for Wireless Personal Area Networks at www.ieee802.org/15, or join the Bluetooth special-interest group at www.bluetooth.org. You can begin your investigation of wireless Ethernet at www.wirelessethernet.org.