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Fixing Drop-Outs with your Airport Base Station

The typical problem is that you're surfing along and all of a sudden, your connection speeds slow to a crawl. The Airport network may pick up speed again at a later point, but you can't figure out why. The most likely user to notice this sort of behavior is someone that transfers large files via a high-speed connection. So what causes drop-outs? Unfortunately, there is no universal answer. There are several possible gremlins at work.

Your Internet connection is flaky
I experienced some strange behavior with my ISP (RCN.net) from time to time where connections also slow down unexpectedly.
  • On several occasions, their network went down and/or got overloaded. The cable coming into our house is somewhat ancient and therefore the cable-modem has trouble from time to time to get it's signal through. Environmental factors outside (rain, wind, etc.) may also play a factor. Naturally, this should not be an issue for those transferring files within their own network (i.e. the data doesn't leave the building).
  • Another source of flaky network connections can be the interaction between the cable/DSL modem and the ABS. For example, to find web-sites like Yahoo.com, your computer looks up the IP address for that site using something called a DNS server. These servers are like giant white pages for the internet, telling your computer where to look for information. If that information is not available to your computer, your web browser will report an error message like Safari can't open the page "http://www.yahoo.com/" because it can't find the server "www.yahoo.com".

    Usually, the interaction between the cable/DSL modem and your ABS works solidly. However, weirdness can and does happen, making access to the DNS servers difficult, if not impossible. Thus, one possible remedy is to look up the DNS servers that your ISP uses and to input their IP addresses directly into the Internet Tab of the ABS, as shown on the following configuration pages: If the DNS servers of your ISP turn out to be unreliable, consider alternates that are not your ISPs. Looking up DNS servers is not that difficult (use Google) but beyond the scope of this guide.
Someone nearby is using the same frequency on their network.
You know, a neighbor who also discovered the joys of a wireless network and is transmitting on the same channel. You can easily discover this sort of problem with MacStumbler (Mac OS X), ClassicStumbler (Mac OS 9), or Netstumbler (Windows). If this was the problem, just note what channel your neighbor(s) are transmitting on, then chose one preferably 3 channels away (there is some overlap between channels)
Someone nearby is using a 2.4GHz telephone
It seems like every portable phone sold today in the US is now operating at 2.4GHz. Unfortunately, these phones have high outputs compared to a ABS and a very long range. Worse, they also tend to skip through various portions of the 2.4GHz frequency band while in use, thus "stomping" on your transmissions in a seemingly random manner. Macintouch has some nice "real world" test results here. Remedies: None other than changing the channel and/or turning on "interface robustness" via the Airport Tab in the Airport Admin Utility.
You are using "Jaguar" (specifically OS 10.2.0) and you have the Firewall turned on.
Our dear friends in Cupertino fixed a lot of bugs and sped things up a bit with the release of "Jaguar", the paid upgrade from previous versions of OS X to 10.2.0. However, they also corrupted the TCP/IP stack somehow so that enabling the built-in Firewall (see "Sharing" control panel) causes the network to drop out. Here, the fix is easy, simply upgrade for free to 10.2.4 or turn off the internal Firewall.
Your ABS may be dying a slow death.
"Graphite" ABS' have a well-documented mode of failure. If the lights on the front are not just green (blinking is OK) during normal operation, your ABS may be on its last legs. Even "replacement" units with Sanyo capacitors have failed due to heat-buildup. If your ABS is dying, try to have Apple replace it as described in the link above. If you have nothing to lose (i.e. Apple refuses to do anything) go ahead and fix the power supply yourself and add ventilation holes while you're at it. Afterwards, the ABS will be cool in more ways than one.
WEP/WPA is on
WEP stands for "wired-equivalent-protection" and is usually a ineffective way to keep determined bad guys out of your wireless network. Worse, besides offering no real protection (unless you invest, maintain additional software and hardware) WEP also has a significant impact on network throughput and stability when run on "Graphite" base stations. For example, one reader at Macintouch found a throughput reduction of 3x with WEP on a "Graphite" base station (Scroll down three articles to the Dec 5 submission from Marigolds from this link). Are more recent PowerPC-based ABS' better at WEP and NAT than the 486 powered "Graphite"? I would think so. But anytime you add more overhead to a transmission cycle (like adding NAT or WEP) throughput should suffer, as you now have more overall data to transmit.
Someone is Free-Riding your connection
The troubles with the security of wireless networks has been well-documented and I won't repeat them all here. Due to the programming efforts of several individuals, even 9-year olds can break into most wireless networks at the touch of a button.

The only reliable way to see who is using your ABS is via some very expensive software packages (Intermapper, et. al). However, you can easily see if someone else is using your ABS by simply putting all your computers to sleep and watching the lights on the ABS. If the lights continue to blink furiously, and no authorized user is using the ABS, then you know by logical extension that there is an unauthorized user. Countermeasures include: enabling Access Control and turning on WEP/WPA or changing the WEP/WPA password frequently.

You may even do something physical, like shielding certain "sectors" by surrounding the ABS antenna with grounded aluminum foil or by buying a directional antenna.

Well, that's it for now on drop-outs. If you know of any other reasons that I may have missed, please let me know via the e-mail address at the bottom of the page

Cheers! Constantin von Wentzel