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Wireless Networking

Wireless Networking
  Technology with Integrity

By Tim Torian, Torian Group, Inc.

 

The use of wireless networking has grown dramatically in the last few years. Wireless standards have evolved, equipment is better and cheaper, and wireless “hot spots” are popping up everywhere. This article is intended to give you a quick overview of what wireless can do for you, and what you should be aware of if you are using wireless networking (wi-fi) at home or at work already.

If you want to understand wireless networking at its simplest level, think about a pair of  walkie-talkies. When you talk into a Walkie-Talkie, your voice is picked up by a microphone, encoded onto a radio frequency and transmitted with the antenna. Another walkie-talkie can receive the transmission with its antenna, decode your voice from the radio signal and drive a speaker.  Wireless networking also uses radio frequencies to connect two computers together in a network: The radios used in WiFi are not so different from the radios used in $5 walkie-talkies. They have the ability to transmit and receive. They have the ability to convert 1s and 0s into radio waves and then back into 1s and 0s. Because they are transmitting at much higher frequencies than a Walkie-Talkie, and because of the encoding techniques, WiFi radios can handle a lot more data per second. As standards have evolved, the speed of wireless has grown. Current standards support speeds comparable to wired networks (wired networks are typically 10 or 100 megabits per second).

Like most computer topics, wi-fi comes with it’s own set of acronyms. There are 3 main wireless standards currently in use. The standards are managed by IEEE and are designed to help vendor’s products interoperate. All the standards are part of the 802. series, which define the physical and logical workings of network devices.

The 802.11a standard transmits at 5 GHz., with up to 54 megabits per second. It is primarily used for specialized commercial applications, and is outside the scope of this article.

802.11b is widely available, inexpensive, and standard on most laptops. 802.11b can handle up to 11 megabits per second (although 7 megabits per second is more typical, and 802.11b may fall back as low as 1 or 2 megabits per second if there is a lot of interference).

The radios used for WiFi have the ability to change frequencies. 802.11b cards can transmit directly on any of three bands, or they can split the available radio bandwidth into dozens of channels and frequency hop rapidly between them. The advantage of frequency hopping is that it is much more immune to interference and can allow dozens of WiFi cards to talk simultaneously without interfering with each other.

802.11g can handle up to 54 megabits per second (although 30 megabits per second is more typical).  802.11g is designed to recognize and interoperate with 802.11b, although you lose the added speed if even one 802.11b device is in range.

Because the  802.11b and 802.11g standards transmit at 2.4 GHz, they are susceptible to interference from wireless phones and microwaves, both of which use this frequency range. They transmit at about 100 milliwatts, which gives them a range of about a block under ideal conditions. Going thru walls, metal structures, and other barriers can reduce their range.  Adding a better antenna can increase the range. 

Some vendors are offering “super-g” wi-fi, which doubles the speed of their product, but is proprietary – you can only use the higher speed with that vendor’s products.

Because there is not much difference in price, any new wireless network should be based on 802.11g. When you look at laptop specifications, this is something to look for. Many laptops are still using the older 802.11b standard.

A wireless “hot spot” is an area which has a wireless “access point”. An access point is simply a radio that connects to wireless devices, and also is connected to a wired network - either a company or home network, or an internet provider’s network. There are many WiFi hotspots now available in public places like restaurants, hotels, libraries and airports.

You create your own wireless network by setting up one or more access points, and transmitting to them with wireless network adapters in computers. Wireless adapters are built in to most newer laptops. They can also be purchased for laptops as a plug in (PCMCIA / Cardbus) card. You can purchase a wi-fi PCI card that is installed in a standard computer, with an antenna that sticks out the back. 802.11g cards are around $50 to $80.

A wireless access point is often combined with a router / firewall to provide an inexpensive solution for home and small business users connecting to the internet. The DSL or cable modem connects to the outside (WAN port) of the device, and the home or office computers connect to the inside (LAN ports). 

On the newest machines, an 802.11 card will automatically connect with an 802.11 hotspot and a network connection will be established. As soon as you turn on your machine, it will connect and you will be able to browse the Web, send email, etc. using WiFi. On older machines you often have to go through this simple 3-step process to connect to a hotspot:

  • Access the software for the 802.11 card -- normally there is an icon for the card down in the system tray at the bottom right of the screen.
  • Click the "Search button" in the software. The card will search for all of the available hotspots in the area and show you a list.
  • Double-click on one of the hotspots to connect to it.

On ancient 802.11 equipment, there is no automatic search feature. You have to find what is known as the SSID of the hotspot (usually a short word of 10 characters or less) as well as the channel number (an integer between 1 and 11) and type these two pieces of information in manually. All the search feature is doing is grabbing these two pieces of information from the radio signals generated by the hotspot and displaying them for you.

Security for wireless devices has gotten a lot of publicity, with good reason. Most wireless access points and routers come set up out of the box to allow anyone to connect. This has created a whole new subculture of people who take laptops with homemade directional antennas in their car and drive around looking for unsecured internet access. This is called war driving.

There are some simple steps you can take to secure your wireless network.

Most wireless access points are managed using a web browser. The first thing to do to secure your network is change the default password used to access the management console.

If you are using Wi-Fi 802.11b or g wireless you can turn on a feature called media access control (MAC) filtering, which wireless Access Points (APs) can use to determine that the wireless devices connected to the network are safe. Every networking device has a unique MAC address, so you can configure your wireless AP to accept only connections from your machines that have wireless adapters.

WEP (Wired equivalent privacy) allows you to encrypt the wireless data, making it harder for an unauthorized wireless user to read your data or connect to your network. Shortly after it was released, there were flaws discovered in the WEP standard. Wireless Protected Access (WPA) is replacing WEP. The standards are not compatible, and your wireless network card drivers (software that runs the hardware) must support WPA as well as the access point or router. WPA only works with Windows XP, and requires a free update to the operating system. (http://support.microsoft.com/default.aspx?scid=kb;en-us;815485).

Many access points will require a firmware update to enable WPA. As usual, the increased security comes with increased complexity. 

For most home and small office users, simply setting up any security will prevent the casual hacker from trying to access your network. The problem has been that most wireless users are not aware that their networks are completely insecure by default.

Although the various vendor’s products are designed to work together, I would recommend sticking to a single vendor where possible. Some of the most popular products are Dlink (www.dlink.com ) and Linksys ( www.linksys.com), which is now owned by Cisco.  We have found that there is a high failure rate in the low end firewall/router/wireless products. If you get one that seems to not work as expected, it may be defective.

For further information and an extensive list of wireless resources, go to www.toriangroup.com/resources/wireless.


Tim Torian teaches computer networking at the College of Sequoias, and has owned and managed several businesses. He is president of Torian Group, Inc. which provides a full range of Technology Consulting services to local business, including computer services, networking, and custom software development. They can be reached at (559) 733-1940 or on the web at http://www.toriangroup.com

     
 

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