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5.2 Commercial Wireless Equipment Overview

With the explosion in Wi-Fi popularity, a
corresponding plethora of vendors and equipment choices have
surfaced. There are an amazing number of access points, but there are
also wireless routers, wireless bridges, wireless-to-Ethernet
bridges, and some Linux-powered equipment as well.

5.2.1 Access Points

In Chapter 1, we covered the basics of 802.11
and the two modes of operation it supports. Infrastructure Mode, the
most common mode, requires the use of a wireless access point.

Most access points on the market share a
common number of connectors: at least one external antenna, one
Ethernet port, status LEDs, and an external power supply or wall
wart. Other features you might find on some models include connectors
for attaching external antennas, a reset button to return the unit to
factory settings, multiple Ethernet ports, and support for
Power Over Ethernet (POE).

Once you get past the outside connectors, the internal features of
access points begin to vary widely. There are all sorts of devices on
the market, ranging from simple home-use devices to enterprise-class
units designed for large deployments. The following list describes
various manufacturers and some of their equipment:

Apple AirPort

This was one of the first access points available. Apple brought this
access point and the AirPort client cards to market before the
802.11b standard was finalized. The internals of the unit are built
by Lucent/Orinoco and are identical to the Orinoco RG-1100. Note that
this applies only to the original AirPort model. The second model
(Snow) and the subsequent AirPort Extreme are based on a different
processor.

Chapter 6 covers some utilities that can be
used to reflash the firmware on these units, allowing you to swap
personalities and even to run Linux on them. As shown in Table 5-2, the AirPort and the RG-1100 are not
configurable out of the box from Linux. This is easily remedied.
Also, early versions of the AirPort had problems with non-Apple
wireless cards. Many of these cards would not associate with the
access point. This has since been fixed through firmware updates.

Orinoco AP-series

This series includes some of the most popular enterprise-class access
points. The AP-500 has a single radio inside, an Orinoco PC Card. The
AP-1000 was the first access point to feature two radios, again both
in PC Card format. Orinoco access points have a wide array of
features: MAC address filtering, network protocol filtering to
enforce such policies as preventing IPX from traversing your wireless
network, support for RADIUS authentication, and custom power over
Ethernet adapters. Orinoco calls these units "Active
Ethernet," and they are available in 1-, 6-, and
12-port models, so that you can power up to 12 access points using
the same POE adapter.

More recent models include the AP-2000, the successor model to the
AP-1000 (which features upgradeability to 802.11a or 802.11g, or
both), giving you a tri-mode access point with all of the Orinoco
features, and the AP-2500, which is a
"hotspot-in-a-box" model that
includes a captive portal and many other features necessary for
setting up a wireless hotspot.

Linksys

Linksys made a huge splash with its WAP-11 access point when it was first
introduced. It had a good feature set and external antenna adapters,
and was priced for the home market. Unfortunately, it is mainly
configurable through a Linksys-specific setup program, which runs on
Windows. There is an SNMP utility for Windows, and Linksys did
publish an SNMP Management Information Base (MIB) for Linux/Unix
users. (An MIB is one or more text files that allow
Linux's SNMP tools to generate human-readable
statistics from SNMP management strings.)

Later Linksys models still continue to ship with Windows-only setup
programs. However, they now offer web-based configuration that is
easily accessible from Linux web browsers.

Much of the other consumer-level wireless gear can be placed in the
same area as Linksys. D-Link, SMC, and Netgear all offer models with
nearly identical features and price points.

EnGenius/Senao

Early in 2002, rumors surfaced of a 200 mW radio card. While one
manufacturer, Zcomax, had made these available, they were hard to
find and were expensive.

At that point, with a few exceptions, most radio cards and access
points were powered by 30 mW radios. You can imagine how excited the
wireless users were at the thought of being able to expand their
range.

Today, EnGenius/Senao offers several access points for indoor and
outdoor use, all with 200 mW radios. Along with Cisco, it is one of
the few vendors to support Telnet access for configuration. Figure 5-1 shows a sample web-based configuration screen
from an EnGenius access point.

Tranzeo

Tranzeo is one of a number of vendors
focused on supplying wireless Internet service providers.
Tranzeo's equipment is designed to work outdoors and
comes in many models, some of which include an integrated directional
panel antenna. Its access points are accessible via Telnet as well as
a Windows-based GUI. Many of its models offer some routing features
(see Section 5.2.2 later in this
chapter).

Cisco

The 800-pound gorilla of networking, Cisco, entered the 802.11 market
when it acquired Aironet in late 1999. Aironet was already a
manufacturer of 802.11 first-generation equipment, and Cisco bought
Aironet at precisely the right time to take advantage of the 802.11b
introduction.

Cisco's access points, as expected, integrate
extremely well into a Cisco network. They have a wide feature set and
compare well with the products from Orinoco in the enterprise space.
Also, as expected, the Cisco units all support Telnet as well as
web-based configuration. Figure 5-2 shows the main
Telnet screen from a Cisco AP.

Figure 5-1. Web-based configuration for an EnGenius/Senao access point

Figure 5-2. Cisco Telnet configuration window

5.2.2 Wireless Routers

The line between an access point and a wireless
router is
very blurry. Many devices sold as access points include routing
features. For example, the Apple AirPort models offer Network Address
Translation and a DHCP server. Wireless routers are basically a
combination of home ADSL/cable routers and a wireless access point.

There are some key differences, however, between most of the wireless
routers now available and standard access points. You can expect to
find at least some of these features on a wireless router:

Routing protocol support

RIP or RIPv2 on many models

Network services

DHCP, DNS, and others

Encryption support

Client or router support for IPSec and PPTP VPNs

Limited firewalls

IP masquerading and some packet filtering

Port forwarding

Sending certain TCP or UDP ports to a specific machine

These units are really designed for home or small-office use.
You'll find that the larger network vendors such as
Cisco don't manufacture this type of hardware,
because they want you to purchase one of their full-fledged routers.

Security in many models of these routers is also questionable. The
bugtraq mailing list at http://www.securityfocus.com/archive shows
you that the number of vulnerabilities in this type of consumer
hardware is fairly high. While these units increase security compared
to a standalone PC connected to a DSL modem, they are not the end-all
be-all for network security.

Wireless routers are available from almost any manufacturer that also
makes access points. An alternative to commercial wireless routers is
to build your own using Linux. Chapter 6 covers
this topic in detail.

5.2.3 Wireless Bridges

Perhaps the most well-known wireless bridge is the Linksys WET-11. A
wireless bridge takes in an Ethernet signal and repeats it out to a
wireless network, and vice versa.

A wireless bridge is not an access point, however. The bridge is only
capable of acting as an infrastructure client to a distant access
point. The practical uses of these devices abound. If you want to
connect your Ethernet-enabled PC to your wireless network, attach it
to a bridge. Wireless ISPs can install a wireless bridge as their
customer premises equipment (CPE), allowing the customer to have a
wired Ethernet network in her home, bridged wirelessly to a remote
access point. Any device with an Ethernet port can be added to a
wireless network using a wireless bridge.

As with wireless routers, most of the companies that manufacture
access points have at least one model of wireless bridge available.
If you want an outdoor wireless bridge with an integrated antenna,
excellent models are available from Tranzeo at http://www.tranzeo.com. Models for home or
office use can be found from Linksys, D-Link, SMC, and all the other
usual suspects.