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Troubleshooting Q&A - December 9, 2004

Should You Ever Switch Wireless Channels?

Your Wi-Fi device may allow you to specify what channel to use for your connection, but would you ever want to change the default configuration? Plus, before you let your guard down, know the risks of playing online games or participating in video chats without the safety of a firewall.

By Ron Pacchiano

Q. I just purchased my first wireless router and it works great. While setting it up I noticed something that I was curious about. One of the configuration options asks you to specify what channel you want to use with your wireless device. By default, it was set to 6, but I noticed that there were a total of 11 channels to choose from. I tired all of them and didn't really notice a difference in the performance of my wireless network. I tired looking in the documentation to see what the significance of each channel was, but it didn't really go into any great detail. So I was wondering, what channel should I use on my 802.11b wireless devices? Is there any advantage to using a channel other then the default? Thanks.

A. Channels are important to understand because they affect the overall capacity of your WLAN. A channel represents a narrow band of radio frequency. Since radio frequency modulates within a band of frequencies, there is a limited amount of bandwidth within any given range to carry data. Therefore it is important that the frequencies do not overlap or else the throughput would be significantly lowered as the network sorts and reassembles the data packets sent over the air.

Knowing that the 802.11a specification operates at radio frequencies between 5.15 and 5.875 GHz, and that the 802.11b and 802.11g specification operates at radio frequencies in the 2.4 to 2.497 GHz range, we can see that the 802.11a has a wider frequency band, allowing more channels and more overall throughput. The wider frequency band allows 802.11a to support up to eight non-overlapping channels. However, 802.11b/g standards support only up to three non-overlapping channels.

Each channel is capable of carrying the maximum throughput for its standard. Therefore, the 802.11b and 802.11g standards have a maximum of three non-overlapping channels, each carrying 11 Mbps throughput (33 Mbps total) and 54 Mbps (162 Mbps total) throughput, respectively. The 802.11a standard has a maximum of eight non-overlapping channels carrying a maximum 54 Mbps throughput each (432 Mbps total). (For more on Wi-Fi standards, check out this Quick Reference guide.)

The frequency ranges and channels may vary by country. In the U.S. there are 11 channels to choose from that the 802.11b (2.4 GHz) standard operate on. All but three of those channels are overlapping channels. Channels 1, 6, and 11 are the only non-overlapping channels. Most manufactures set their default channel to one of the non-overlapping channels. D-Link products, for example, default to channel 6. You have the option of selecting which channel your WLAN operates on in order to avoid interference from other wireless devices that operate in the 2.4 GHz frequency range. Examples of this would be 2.4 GHz cordless phones and X-10 wireless products.

The biggest advantage of 802.11b is that it's the most widely deployed wireless LAN technology and provides good wall penetration and indoor range. The advantage of 802.11a is that it provides increased network capacity and interferes with other wireless devices far less than 802.11b products do.

So to answer your question, unless you have a specific reason for changing it, I would suggest you keep your wireless channel configured for the manufacturer's default settings. If, however, you must change it, for the best performance I would suggest trying to use one of the other non-overlapping channels first: Channels 1, 6, and 11. Other then interference issues, there really is no other reason or advantage to selecting another channel.

Q. I have a few friends who are away at school and every once in a while we like to get together and chat via a video conference or just play a few games online. Unfortunately, my firewall prevents those applications from functioning. Usually when I want to do one of those things I have to disconnect my PC from the router and plug the WAN line directly into my PC. This is a real hassle. I have a NetGear firewall router and I was wondering if there was a way to completely disable or turn off the firewall functionality on my router? Thanks.

A. You didn't mention specifically which router you had, but in my experience you cannot disable the firewall on the router. You can disable a software firewall (e.g., ZoneAlarm), but not a hardware based one. Most routers use NAT (Network Address Translation), which allows multiple hosts to share a single IP address and make many concurrent connections. If this feature was disabled you wouldn't be able to get more then one PC online. However, even if you could disable it, why would you? In this day of identity theft and Denial of Service attacks you should NEVER be online without some type of firewall running. That's just asking for trouble.

Since so many applications require access to certain ports to function properly, firewalls give you the capability to define rules for managing the network traffic that tries to come into the system over those ports. In most applications, port usage is clearly defined, making it easy to know which ones to open.

However, some applications, like your video conferencing software, make use of so many dynamic or changing ports, that it makes it very difficult to get them to work correctly through a firewall. In this situation it might be simpler for you to just place your PC TEMPORIARILY into your router's Demilitarized Zone (DMZ).

The DMZ is essentially the equivalent of you plugging your PC directly into your Internet connection. It is completely unprotected and allows unobstructed access to your PC. This is basically what you're doing now; except you don't need to actually unplug anything. You only have to change your PC's IP address to the one that has been assigned to the DMZ. Most routers will allow you to define only one. Just remember to change your PC back to a protected IP address after your finished using it. For the record though, I would only do this as a last resort.

Your router's documentation can show you how to go about correctly opening ports and configuring your DMZ.

I hope you find this helpful. Good Luck!

Use our feedback form to submit your questions on home or SOHO networking issues. We cannot guarantee to answer every question we get, but we’ll consider them all. Earthweb HardwareCentral earthwebdeveloper CrossNodes Datamation

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