Section 10.2. Today s Wireless Infrastructure

10.2. Today's Wireless Infrastructure

Many network administrators and most home users have the belief that setting up a wireless network is a self-managing affair. Wireless cards are available for most computers. The thinking in many facilities today seems to be: "Throw in the wireless cards, and you are off."

This is called an ad hoc infrastructure. Sure, wireless will work under these conditions but to do so is to invite a security disaster. In this arrangement, units attach freely to each other, and there is no central authority to govern authentication (see Figure 10-1).

Figure 10-1. Wireless architectures

In contrast, an infrastructure architecture is a wireless network in which all units communicate with one unit that connects to a wired network. Wireless access points (APs) provide an interface between the physical network and the various computers containing wireless cards. This makes sense; after all, most people use wireless not to connect to each other, but to a LAN, or to the Internet.

Infrastructure architecture improves security and performance because administrators can monitor central login points to detect illicit access attempts. This architecture also makes network resources available to wireless users in the network, which increases the value of the connection.

Each network attachment point and the area it serves is called a basic service set (BSS). If it exists alone on a network, it is called an independent service set (ISS). Two or more basic service sets can exist on the same wired network. Traffic hands off between them depending on which has the stronger signal; this process is called roaming.

It is possible to take advantage of wireless to overcome an impassible barrier between two network segments. Used in this way, wireless equipment forms a network bridge. Most access points will function as bridges; however, if the interconnection is between two buildings, there may be an advantage to using specialized hardware that is optimized to withstand exposure to the elements.

Home users too have pined for the advantages of a wireless world. Even something as simple as working one's laptop while watching a TV show used to require stringing a long network cable across the floor. This was a trip hazard at the least, and such a cable was often a luxury in its own right. Well-wired houses can be a rarity. The time and tools required to route wires through walls made it a daunting task. A wireless access point connected to a cable or DSL modem makes wireless highly desirable for home use.

10.2.1. Wireless Costs

Wireless was formerly an expensive and cumbersome solution. Until it became possible to lower its cost and increase its performance, wireless in data networking remained an expensive niche solution, justified only in a few unusual circumstances in which running cable simply was not feasible. These usually took the form of bridge links between buildings or floors.

With the adoption of the IEEE 802.11 series of standards in 1997 and subsequent updates, practical and easy wireless networks became available at reasonable cost. Wireless suddenly found a place in corporate networking and coffee shops, public places and poolsides. Anywhere you desired network computing without the necessity of running cables first, wireless hit the ground running. Although there are many forms of radio and light wave communications that can be called "wireless," wireless systems, or Wi-Fi, usually refer to those that align with the 802.11 standards.

Radio Rundown (Wireless Words)

Standards for Wi-Fi communications systems are put forth by the IEEE and licensed by local governments. The IEEE 802.11 family of equipment operates in the unlicensed portions of the 2.4 GHz industrial-scientific-medical (ISM) band and 5 GHz unlicensed national information infrastructure (UNII) radio bands.

The original wireless, IEEE 802.11, an old 1-Mbps service, has largely been superceded by 802.11b, which operates at 11 Mbps on 2.4 GHz. The newer IEEE 802.11a system operates at 54 Mbps on 5 GHz. In June 2003, the IEEE 802.11g standard was formalized. This standard put the superior 802.11a transmission scheme onto the friendlier 802.11b frequencies, allowing 54 Mbps on 2.4 GHz as well, although most 802.11g units maintain backward compatibility to 802.11b, and multiband radios are available. The IEEE 802.11n standard offers increases in range and significant increases in speed over a, b, or g. The new IEEE 802.11i standard adds security to the 802.11 series, helping to plug a serious deficiency. Here are some other versions of radio communications:

Fixed microwave

Licensed channels link at various frequencies. The low-cost, license-free 802.11x systems are a direct response to the difficulty and expense of these services, but a license carries the advantage of legal protection against interfering services.

Multi-Channel Multipoint Distribution Service (MMDS) or "wireless cable"

This repurposing of terrestrial microwave channels, including the instructional television fixed service (ITFS), is used for schools.

Local Multipoint Distribution Service (LMDS)

A wireless competitor to fiber optic to the pedestal (FTTP), LMDS is a licensed service that operates in the 28-31 GHz band to carry voice, video, and high speed data communication.

Satellite

Commercial satellite data services have existed for years, often using very small aperture terminal (VSAT) antennas, which were precursors to the small antenna satellite systems available for homes. Satellite home video services usually offer a data capability as well.

IEEE 802.15 (Bluetooth) wireless personal area network (WPAN)

This system offers low complexity and low-power short-range connectivity for personal devices and peripherals. Many systems use Bluetooth to synchronize PDAs and their desktop computers.

IEEE 802.16 wireless metropolitan area network (wireless MAN or WiMAX)

These licensed and unlicensed broadband wireless access systems operate in a variety of frequencies as an alternative to fiber optic for last mile distribution to businesses.

Infrared

Infrared offers generally low bandwidth line of sight communications for control devices, such as TV remote controllers.

Free-space laser

These systems offer lightwave-based license free communications and are an alternative to fixed microwave.

There are real advantages to wireless. Without it, the work area outlet near your desk (the RJ-45 connector where you plug your computer in) is served by a consolidation point, which leads to a telecommunications room, where it ends on a patch panel before being wired into some kind of expensive equipment, such as a switch or router. This orderly structured cabling system is designed to be durable, reliable, and serviceable, but at a price of flexibility and spontaneity. It is literally built around a concept of servicing a work area, not a person. Different people may come and go, but the work area remains the same.

In contrast, wireless sort of justwell, connects. You loft a signal from your computer, and if you are within radio earshot of the access point, you are asked to authenticate (provide your username and password), and then you are on the air, or attached. You are connected at a speed of anywhere from one-half to about three times that of a 10BaseT (10 megabits per second) LAN, depending on the flavor of 802.11 used, and you can sit wherever you please and move about at will.

But wireless is fraught with dangers that come from not being tied to a cable. Unauthorized users can attempt to make connections in your name without having to set foot within your walls. If they get in on your radios, they can use up bandwidth, access files without proper identification, and potentially gain a free rein on your network and beyond. Wireless provides a modern-day version of the old problem of users installing unauthorized modems on their desktop PCs. And regardless of whether they can actually attach to your network, they can still eavesdrop freely without making a connection, something that is difficult, though not impossible, to do with wired networks. That is the trade off of wireless; you can get high speed and easy connection with great easebut so can everybody else.

Too Free Access?

I was once on a job site in a large office park where a local affiliate of a large chain was replacing their main data link to the corporate offices in the East. The plan was to connect two wireless access points to a router, which connected via a T-1 link to the corporate headquarters. A firewall was employed to keep outsiders out. Because of a glitch in the service provider's programming, we could not turn on our system and provide service as planned. After an hour or so, the provider corrected the issue. We then went to apologize to the branch president, who had anticipated using his new wireless laptop card to browse the Internet over lunch. His response was a lecture in wireless security packed into one sentence. "Is there something wrong?" he asked. Although our own system was down, he had not missed a beat. There were enough carelessly secured wireless access points operating in the surrounding businesses that he never lacked connectivity. Good for browsing, but bad for those businesses.