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I have a cable modem with a standard Linksys wrt54g wireless connection attached to it. There are about eight wireless devices in the house attached through this network. The devices include a Mac, Windows XP machines, iPhones, a printer, and a Tivo.

Starting about a month ago the network regularly and often slows down. You can be surfing the net just fine and suddenly things come to a crawl for about a minute or so, and then they pick back up again.

As I can't predict when the slowdown will occur, diagnosing the problem has been difficult. Luckily the other day I had two computers in close proximity and noticed that when the slowdown happened, they were both affected the same way for the same time. To the best of my knowledge, no single device is doing a large download when the slowdown occurs.

I would like to call the internet provider and complain, but I am not sure that the problem isn't one of the computers in my house using all the bandwidth and not them. Anyone have an idea how to track this down?

Thanks in advance.

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3 Answers

up vote 2 down vote accepted

From my own personal experience I can tell you the two most likely culprits.

Since you are using a wireless router you have the likely issue of interference. FCC rules basically state that your device must accept interference even if it causes undesired behavior. Being that these devices use an unlicensed band, you can never be sure when someone starts transmitting on the same channel you are using. So to that end a wireless "site survey" is in order. There are some very sophisticated tools for this purpose but those tools get a bit pricey. So this is the poor man's site survey method....

Within your wireless network utility pull up the connection manager and get it to show you the networks within range. Each utility is a bit different but they all generally have the same functionality. Be sure to take notice of the signal level and the channels that are in use. Any channel you see in use is most likely a channel you want to avoid. So lets say if you are on set to use channel 6 and you see another SSID also using channel 6, you would want to change your channel to one that is not in use. Depending on the population density around you, you may have lots of interference or not much at all.

Keep in mind that the best channels to use are 1, 3, 6, 9 and 11. These channels do not overlap with one another and you stand the best chance of getting good results.

Cutting the interference usually solves the problem you have.

Another thing to consider is that your upstream provider may be having issues. Cable modems use a shared medium, so high usage in your neighborhood might just appear as such a problem as your connection slows down as a result.

Comcast is particularly noteworthy as their network seems to mulfunction all throughout the day. I determined that Comcast's DNS servers were not responding and my pages would time out trying to load. I set my connection to use external DNS servers located on the internet to bypass the flakey DNS from comcast.

This is a good bit of info, but should give you something to get started with.

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There are at least 6 wireless networks in the area. I surveyed the area and switched to channel 1. Things seem better so far. Thanks –  Michael Groner Jul 28 '09 at 14:10
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I haven't used it myself yet, but I keep hearing that WireShark is the program of choice to diagnose Network Issues.

-JFV

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I agree with JFV. Wireshark is one of the best tool for the job for network slowdowns. It may be a good tool to check if anything in your network is using the bandwidth unexpectedly without you noticing. I am also having the same issue, but I'm thinking about calling the ISP for a better understanding of whats going on.

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I'd suggest would have been better posted as a comment to @JFV's answer so I'm afraid -1, though the downvote should be deleted if removed as 'not an answer'. –  pnuts Dec 1 '12 at 8:24
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