O'Reilly Book Excerpts: Wireless Hacks
Do-It-Yourself Access Point Hardware
Editor's note: Rob Flickenger is back this week with another excerpt from his latest book, the recently released Wireless Hacks. Like the title of this hack says, Rob offers do-it-yourselfers four PC-compatible hardware solutions you can buy--without breaking the bank--to build and run your own custom access point.
Hack #51. Do-It-Yourself Access Point Hardware
Use one of these popular embedded PC boxes as a building block for your access point project.
There is a huge variety of PC-compatible hardware available that is perfectly capable of serving as an access point. If budget is a concern, you can certainly dust off that old PC that is collecting dust in the closet (provided that it is roughly of 486/50 vintage or so; 386 machines, while nostalgic, are probably too painfully slow to deal with by today's standards). Some people choose to use a full-blown tower case with an old 486 or Pentium processor as a combination access point and file server. One node on the NoCat network is an old Apple G3 running Yellow Dog Linux, as that was what we had lying around!
But if you are planning on building out a large network project, it is advisable to standardize your hardware platform. This is a good idea from an aesthetic point of view, as well as for reliability and ease of troubleshooting. While your dusty old 486 might be just taking up space, brand new embedded machines are coming down in price. These are tiny, fanless machines that are designed to run off of DC power, which boot from cheap compact flash RAM. This means no moving parts, simple ventilation requirements, and potentially very long uptimes.
Not all embedded solutions are necessarily cost effective. One notorious example is the PC/104 hardware used in industrial applications. Although it offers relatively low performance, this hardware has a reputation for robustness and ease of programming, as well as the standard PC/104 "stackable" bus. But even its extreme popularity in the industrial world hasn't done much to bring down its price, relative to what is available in the general purpose computing world.
Whatever hardware platform you choose, be sure that it meets your needs. When choosing a piece of hardware, you should remember to consider the number and type of radio and network interfaces, cooling and power requirements, size, RAM and CPU available, and of course, cost. Here are a number of solutions that DIY networks have found to bring a high performance-to-price ratio.
- Soekris (http://www.soekris.com/)
Affectionately known as the "little green box," the Soekris solution is a popular choice among do-it-yourself networkers. There are a number of Soekris models that work well as access points, with and without PCMCIA. All Soekris boards will boot from Compact Flash and come standard with multiple Ethernet interfaces, a mini-PCI slot, hardware watchdog, serial console, and an AMD 133 MHz processor. They are all fanless boards and use a DC power supply (see Figure 4-11).
Figure 4-11. The Soekris net4521.
At the time of this writing, the Soekris net4521 (with two PCMCIA slots, two Ethernet ports, a mini-PCI slot, and 64 MB RAM) sells for about $250.
- OpenBrick (http://www.openbrick.org/)
Another popular embedded solution is the OpenBrick. The typical OpenBrick has a 300 MHz (fanless) Geode processor, an on-board NIC, a PCMCIA slot, and boots from Compact Flash. It runs on DC power, and unlike the Soekris, also has USB ports (although it does not have a mini-PCI slot.) It comes standard with 128 MB RAM, and also has room for a 2.5" hard drive.
The OpenBrick (Figure 4-12) is designed to serve as a tiny server or client workstation, and as such, has virtually all standard PC functionality (VGA and NTSC video out, PS/2, parallel and serial ports, audio, etc.). Its additional features also make for a higher price tag, with the going rate about $360 as of this writing.
Figure 4-12. The OpenBrick.
- Via-based computers (http://www.via.com.tw/)
There are a number of Via-based computers on the market. They are generally marked as desktop PCs, although small, fanless cases that take a DC power supply are becoming commonplace. As they are intended to be used as general purpose PCs, they typically have 500 MHz or better Via processors, on-board NICs, an IDE interface, USB, and a PCI slot. Using an inexpensive CF-to-IDE adapter [Hack #52], these boards (or, indeed, any PC) can be made to boot from Compact Flash for a hardware solution with no moving parts.
If you are looking for a fanless solution, be sure to get the 500 MHz version, as the 800 MHz and faster Via boards require a processor fan. Via motherboards (Figure 4-13) are around $100 at the time of this writing, without case, RAM, or storage.
Figure 4-13. A Via EPIA 800MHz PC.
- The Fujitsu Stylistic series
This collection simply wouldn't be complete without mentioning the Fujitsu Stylistic 1000 series (Figure 4-14). This is a very popular surplus market tablet PC that has "hack me" written all over it. It has three PCMCIA slots, one of which is the boot device. It can boot from Card Flash using a CF to PCMCIA adapter, and is unique in that it has an integrated LCD display and battery. The 1000 series has a 486 DX4/100 processor, is expandable to 40 MB RAM, can use a cordless pen for input, and has served just fine as a hardware gateway (I use one myself for my node on SeattleWireless). Fujitsu still makes the Stylistic series, although new machines are quite expensive (on par with modern laptops). The older 1000s or 1200s can frequently be found on the surplus market for less than $100.
Figure 4-14. The Fujitsu Stylistic 1000.
Running your own custom access point can be considerably more challenging than the plug-and-play devices you can buy in consumer electronic stores, but building such devices can be much more rewarding as well. Bringing the power and flexibility of Linux or BSD to the access point itself can lead to all sorts of interesting possibilities that just can't be accomplished with a $75 over-the-counter access point.
Be sure to check back to this space in two weeks for another hack from Wireless Hacks on enabling BSS master mode on Hermes-based radios.
O'Reilly & Associates recently released (September 2003) Wireless Hacks
- Sample Hacks are available free online.
- You can also look at the Table of Contents, the Index, and the full description of the book.
- For more information, or to order the book, click here.
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