Security

WLAN issues that require consideration

The four big WLAN issues

In the almost two years since our first look at the basics of wireless networking, WLAN technology has come a long way. Prices have fallen drastically, wireless encryption protocol (WEP) security is more widely supported, and components tend to be more reliable and have a longer range, yet there are still many different factors to consider when deciding whether or not to go wireless. You must look at cost, reliability, speed, and of course, security.

Getting connected
Wireless networks function similarly to wired ones. However, where wired networks use cables to attach a NIC card to a hub, a wireless network uses wireless NIC cards to connect to an access point. A wireless NIC card is a NIC that’s equipped with a transceiver and an antenna. An access point is a wireless hub. Generally speaking, most access points also contain an RJ-45 port that allows them to act as a gateway between a wired and a wireless network.

Technically, a wireless network doesn’t require an access point. If you need only a few wireless workstations, they can run in what’s known as Ad Hoc mode. Ad Hoc mode allows a wireless NIC to communicate directly with another wireless NIC without the aid of an access point. But if you plan to use more than two or three wireless clients or if your wireless clients will require access to a wired network, you’re better off running in Infrastructure mode than Ad Hoc mode. Infrastructure mode uses an access point.

Each access point has specific capabilities that you need to be aware of. First, it has a coverage area known as a cell. Traditionally, access points have a coverage area of between 150 and 300 feet in every direction. But in recent months, access points have come onto the market offering ranges of up to a mile. Special outdoor access points with large antennas can offer a range of several miles. Of course, obstacles such as trees and buildings decrease the range and also the size of the cell. Indoors a cell's size also depends on the construction of the building. Radio signals will travel through walls, ceilings, and floors, but these obstacles can seriously degrade the signal's strength.

You must also be aware of the number of simultaneous sessions an access point can support. At the time the article above ("Considering the jump to wireless networking? Here's an overview") was written, a high-end access point typically supported about 64 sessions. Today, most access points support 256 sessions.

Multiple access points
A single access point may not be adequate for a large organization. The access point may lack the necessary range or may not support enough users. Fortunately, you can use multiple access points to add extra range and support. When multiple access points are used, the cells tend to overlap. This allows wireless users to roam from one cell to another without loosing connectivity. A wireless network consisting of multiple cells works similar to a cellular telephone network; when a user’s signal begins to fade, another access point with a stronger signal takes over.

Multiple access points can also be used for load balancing. By using multiple access points, you can split the network traffic into two or more cells, rather than having a single cell congested with all of the traffic.

Staying secure
Perhaps the biggest concern about wireless networks is security. After all, if your company uses wireless networking, someone could sit in the parking lot with a laptop and steal packets of data out of the air. This is where WEP comes in. WEP is a shared key encryption protocol for wireless networks available in 40-, 64-, and 128-bit encryption strengths. Typically, using WEP has only a small negative impact on throughput. In tests that I've conducted, enabling 128-bit WEP seems to reduce throughput by about 300 Kbps..

Cost
Although going wireless may cost a little bit more money up front than implementing a wireless network, the wireless network will save money if the company moves locations, because the company won’t have to leave behind existing wiring and go wire a new building. Instead, the company could just pick up the access points and go.

Wireless access points are actually cheaper to implement than wired hubs. At the time that this article was written, a 24-port 3Com 10/100 hub cost just under $400. If you wanted to connect 256 users, you’d need 11 of these hubs for a total price of about $4,400.

In comparison, wireless access points that support 256 wireless clients cost between $200 and $400, depending on the features that you want. Many access points even include features such as DHCP servers, firewalls, and broadband routers. Something that you must keep in mind as you look at the price difference, though, is that although wireless access points are cheaper than wired hubs, wired hubs are much faster. For example, the wired hub that I priced can run as fast as 100 Mbps. Most 802.11B wireless access points are only rated at 11 Mbps. I review a lot of access points for an independent research firm, and in real world tests, I’ve never seen a wireless access point run faster than 5 Mbps.

Also, wireless NICs are a little higher than wired NICs. A PCI-wired NIC costs about $20 while a wireless PCI card costs about $100. A PCMCIA version costs about $150.

Reliability
Although wireless networks are more reliable than ever before, there are still times when reliability is a factor. Wireless networks (of the 802.11B variety) run on the 2.4-GHz frequency, just like high-end cordless phones. My network tends to slow to a crawl every time I use one of my cordless phones. I have three other 2.4-GHz cordless phones that don’t cause interference problems, though.

Wireless access points allow you to select from a number of channels, but even if you happen to find a channel that always works, your network could experience the problem that I just described if the office next door gets new cordless phones.

Another source of wireless network interference can be background radiation. For example, for a while I had a PC with a wireless NIC in my kitchen. The PC would have problems with interference every time that I used the microwave. So make sure your office kitchen isn't too close to your wireless network.
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