WHy does Windows periodically decide it can't find the internet?

November 17, 2005 11:11 AM

Why does my Windows XP laptop keep losing the internets?

Seemingly randomly, Windows decides it can't resolve domain names. This could be immediately after bootup, or more often, after a few hours of use. Filesharing programs like Azureus seem unaffected - their downloads/uploads continue. But browsers simply stop working, and pop up "Domain cannot be found" when I'm trying Gmail.com etc. In fact, I've noticed that the problem seems to be more frequent when I have a lot of P2P connections open. Could this be consuming some sort of Windows resource, and preventing other apps from making DNS queries?

It happens irregularly but often, like once a day. A reboot of the laptop usually fixes things, but logging in and out of any account doesn't.

Also, occasionally the signal strength of my wifi connection drops to near zero, even when the laptop is mere inches from the router. This doesn't happen often, and is again remedied by similar sledgehammer tactics.

I have no idea how to get into the bowels of Windows to debug, so any pointers to useful tools will be greatly received. Maybe it's time to put this box out of it's mysery and install a real OS :-)

Setup is:

Windows XP on a Clevo notebook

Belkin wireless USB adapter (model num F5D7050)

Buffalo Airstation WMR-G54

ISP is Zen ADSL

Thanks for any suggestions.

posted by ajp to Computers & Internet (12 answers total)

I am not a TCP/IP ninja, but some ISPs or OSs will limit the number of TCP/IP connections you can have. When I was running Windows XP, bittorrent would often slow my web browsing for a halt. Your computer needs to contact a DNS server to resolve IPs, and maybe it can't with so many (and so bandwidth consuming) P2P connections. A robust client, like BitComet, will let you limit the number of connections and/or the total bandwidth. Tweak!
posted by ori at 11:24 AM on November 17, 2005

Turns out it's Azureus.
posted by ori at 11:26 AM on November 17, 2005

"Windws XP SP2 introduces a few new twists to TCP/IP in order to babysit users and "reduce the threat" of worms spreading fast without control. In one such attempt, the devs seem to have limited the number of possible TCP connection attempts per second to 10 (from unlimited in SP1). This argumentative feature can possibly affect server and P2P programs that need to open many outbound connections at the same time."

(more info, and ways to remove the cap)

And two more links specific to Azureus:
More info. More info.
posted by ori at 11:30 AM on November 17, 2005

I believe I have a similar problem (my roommates have it as well). We'll be surfing the internet and our HTTP port will quit responding. Then any other new processes that we attempt to start (Instant Messengers, P2P, games, etc) will not connect. Only a reboot will fix it. It usually happens when too many tabs are opened too quickly in Firefox, but it occurs randomly just as often.

It makes me wonder if its some kind of anti DoS measure our ISP has in place, or what.
posted by mhuckaba at 11:53 AM on November 17, 2005

I had a similiar problem. I fixed it by typing in my DNS IPs directly into my router rather than having it autodetect my DNS servers.

YMMV.
posted by TheAnswer at 12:11 PM on November 17, 2005

Sounds like the router's NAT table space could be filling up. You could try a daily power cycle of the router. Good programming would keep it pristine, but this is rarely executed well, and with BT many, many connections seem to overwhelm the ability of low-end routers with limited RAM to keep up.

Also, the drop outs could be down to something as simple as close proximity to a cordless phone or a microwave oven...
posted by meehawl at 12:19 PM on November 17, 2005

My home config does this as well. I find the solution is to go to a Command Prompt (Start > Run > cmd.exe) and execute the following:

ipconfig /release
ipconfig /flushdns
ipconfig /renew

After which I wait a few seconds and try again. This fixes the problem 99% of the time, and repeating the procedure/waiting slightly longer remedies the remaining 1%. It's probably easiest to put these commands into a batch file which can be run at will.
posted by Danelope at 1:02 PM on November 17, 2005 [1 favorite]

maybe not helpful, but two things i've come across:

- a competing wireless network somewhere nearby

- if i have more than one user account on the same computer logged in at the same time and, say, messenger or something like that is open in both, my connection goes on and off, as if the two accounts are competing for it; i don't know if this is actually what is happening, but i avoid it in any case
posted by troybob at 2:29 PM on November 17, 2005

In my experience the problem is that you're p2p uploads are set too high. When you are using all of your upload bandwidth your download bandwidth will choke and die. Its dumb that for optimal downloads you have to have some unused upload bandwidth but that's the way it is at least in the US. If youve got broadband you probably have 256k upload which is 25k to a program like azureus (1mbs would be 100k and etc). You want to set it like 1/3-1/4 of what your max is and that is divided between everyone running p2p. I've noticed az will ass out the net for everyone even when set to 5k so maybe try something like utorrent or emule? Usually after it times out you can refresh the link and itll come up the second time around albiet but slowly.
posted by psychobum at 2:49 PM on November 17, 2005

Response by poster: Thanks for the tips. The P2P stuff is definitely interesting. However, it happens even without Azureus running, just with Firefox open.

Okay, so it just happened right now :-)
Metafilter could not be found. Bummer.

So I disconnected from my wireless network, then reconnect, using the Wireless Network Connection panel after right-clicking the tray icon. But to no avail. The internet has vanished. I'll be pasting this in after a reboot.

I'll have a poke around the speedguide.net site, thanks ori.

I have thought about hard-coding IPs into the Win equivalent of resolve.conf but that is a really rubbish workaround. And I somehow doubt it will work anyway.
posted by ajp at 4:38 PM on November 17, 2005

By the way, Azureus is a resource hog. If you're on Windows, try BitComet - it's a much lighter BT client, and does proper BT-compatible distributed hashing.
posted by meehawl at 5:04 PM on November 17, 2005

You wouldn't happen to have an ACTIONTEC router, would you? Because I have the exact same problem, and I tracked it down to the router assigning DNS to itself and acting as a sort of DNS gateway. The problem is that after a random period of time, the router becomes flaky and not only randomly disconnects the wireless network, but fails to accept DNS connections anymore (although other TCP/IP traffic is unaffected).

For now, I manually set the DNS servers on my laptop.

For the wireless, "net stop wzcsvc" stops the zero-configuration wireless service, which can smooth out the bumps in flaky wireless connections. For example, if the wireless signal is lost for a few seconds, with wzc on, the machine will disconnect and find someone else's network. But when it's off, it won't do anything, and eventually regain the connection (of course, you eventually need to turn it back on to change networks).
posted by helios at 7:33 PM on November 17, 2005